Help for Foxhound 4.0.4740a

Table of Contents     [RisingRoad]


Foxhound 4 

5. The Connection History Page

The Connection History page shows the connection-level performance statistics for a single connection, as well the server and database-level statistics corresponding to the top-most row in the connection section.

The Connection History page is similar to the Connection section of the Database Monitor and Sample History pages, except that multiple samples for a single connection are shown rather than multiple connections for a single sample.

In other words, you can use the Connection History page to see the history of a single connection at a glance, rather than having to jump from page to page (sample to sample) on the History page and then scroll to the connection you're interested in.

The Connection History Page is displayed for target databases running on SQL Anywhere 9 and later.

5.1 The Connection History Menu

5.2 Top Sample

5.3 Connection Identification

5.4 Connection Samples


Foxhound 4 5. The Connection History Page 
5.1 The Connection History Menu

Back to Menu    xxx (DSN)    New Menu    Schema    Monitor    History    Foxhound Options    Monitor Options    About  -   Mmm Dd yyyy...   

The Back to Menu link displays the main Foxhound menu page in the current browser window or tab.

The DSN: / Connection String: title shows the name of the DSN or Connection String that you used to connect to the target database. This identifies the "current target database", a term used in this Help.

Multiple Connection History pages that display the same DSN or Connection String show the same data; they do not represent separate sampling sessions.

The New Menu link opens the main Foxhound menu page in a new browser window or tab.

The Schema link opens the Display Schema page for this target database in a new browser window or tab.

The Monitor link opens the Monitor Database page for this sampling session in a new browser window or tab.

The History link opens the Sample History page for this sampling session in a new browser window or tab.

The Foxhound Options link opens the Foxhound Options page in a new browser window or tab.

The Monitor Options link opens the Monitor Options page in a new browser window or tab.

The button is a context-sensitive link to this Help topic. This button appears in many locations, each of them a link to a different Help topic in this frame.

Tip: To hide the Help for every new page, see the Show Help section on the Foxhound Options page.

The About link opens the About Foxhound page in a new browser window or tab.

The Mmm Dd yyyy... timestamp shows when this Connection History page was displayed.

 Newest    500    100    20    1 sample     Message
 Month    Week    Day    3 Hours    1 Hour

Newest - Scroll to the most recent samples for this connection

Tip: Click on Newest to scroll to the "new top". If sampling is running, new samples will continue to be gathered, and the Connection History page won't automatically show them unless you scroll up.

500 - Scroll up by 500 to more recent samples for this connection

100 - Scroll up by 100 to more recent samples for this connection

20 - Scroll up by 20 to more recent samples for this connection

1 sample - Scroll up by 1 to more recent samples for this connection

Message - Scroll up to the next most recent sample that has an Alert, AutoDrop or other message

Month - Scroll up by one month to more recent samples for this connection

Week - Scroll up by one week to more recent samples for this connection

Day - Scroll up by one day to more recent samples for this connection

3 Hours - Scroll up by three hours to more recent samples for this connection

1 Hour - Scroll up by one hour to more recent samples for this connection

Message     1 sample    20    100    500    Oldest 
        1 Hour    3 Hours    Day     Week     Month      Go to: 

Message - Scroll down to the next older sample that has an Alert, AutoDrop or other message

1 sample - Scroll down by 1 to older samples for this connection

20 - Scroll down by 20 to older samples for this connection

100 - Scroll down by 100 to older samples for this connection

500 - Scroll down by 500 to older samples for this connection

Oldest - Scroll down to the oldest sample for this connection

1 Hour - Scroll down by one hour to older samples for this connection

3 Hours - Scroll down by three hours to older samples for this connection

Day - Scroll down by one day to older samples for this connection

Week - Scroll down by one week to older samples for this connection

Month - Scroll down by one month to older samples for this connection

The Go to: field lets you scroll to a specific sample date/time or sample number. You don't have to be precise, the Connection History page will scroll to the point nearest the value you typed.

The Go to: value is checked to see if it's a valid number first, then a date/time, so "Go to: 20120601" interpreted as a sample number rather than a sample date/time.

Go to: 1 works like Oldest.

Go to: 0 works like Oldest.

Go to: -1 is ignored, as are all values other than non-negative integers and valid date/times.

Go to: 1901-01-01 works like Oldest.

Go to: 9999999999999 works like Newest.

Go to: 2999-01-01 works like Newest.


Foxhound 4 5. The Connection History Page 
5.2 Top Sample
Top Sample

Interval

Response... Heartbeat, Sample, Ping

Throughput... Req, Commits, Bytes

Conns / Parent, Child Conns

Executing, Idle, Waiting Conns

Active Req, Max Req, Unsch Req

Locks Held, Conns Blocked, Waiting Time

CPU

Temp Space, Rollback Log, Uncommitted

Cache Panics, Low Memory, Satisfaction

Checkpoints, Checkpoint Urgency, Recovery Urgency

Disk/Cache: Internal Index, Leaf, Table

Incomplete Reads, Writes

Disk Reads, Disk Writes, Log Writes

Index Adds, Lookups, Satisfaction

Full Index Comps


Foxhound 4 5. The Connection History Page 5.2 Top Sample 

The Top Sample section shows the database sample data corresponding to the top-most Connection History sample.

The Top Sample section consists of 4 or 5 lines:

Performance Tip:

The other columns are highlighted according to the values in the Peaks section (shown on the Sample History page), as follows:

Dashes "-" are displayed for omitted column values instead of empty spaces. This makes it clear which values are not available or not applicable, and it also makes the resulting text somewhat easier to read when you use copy-and-paste. For example, the "CPU" percentage appears as a dash "-" for the first sample because it can only be calculated for second and later samples.

Note: This use of dashes "-" does not apply to columns which have been entirely omitted because the data is not available for the version of SQL Anywhere being used for the target database; e.g., the "CPU" column does not appear at all for version 5 and 6 target databases.

Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Top Sample
The Top Sample column shows the date/time that Foxhound recorded the topmost successful sample.

Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Interval
The Interval column shows the actual time interval between the previous sample and this one.
Foxhound tries to record a new sample every 10 seconds but the actual interval can vary.

Foxhound uses the interval time to convert performance statistics from cumulative counts to rates; e.g., to convert the total number of disk writes into the number of disk writes per second.

A very long interval like 1h 19.8m may indicate the computer was in sleep, standby or hibernate mode.

See also Alert #1 Database unresponsive.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Response... Heartbeat, Sample, Ping
Response time, also known as latency or access time, is a measure of how long it takes the database to respond to a single request:

The Response... Heartbeat time column shows how long it took for Foxhound to execute the SELECT * FROM DUMMY heartbeat or "canarian" query.

Performance Tip: Heartbeat time should be very small. Repeated values larger than 1s may indicate a performance bottleneck, and sudden increases in value may indicate a period of non-responsiveness.
Note that there's a difference between precision and accuracy; for example, two successive Heartbeat measurements like 25ms and 50ms may be very precise but they may not accurately represent an immediate 100% slowdown in performance.

On the other hand, a long period of Heartbeat values averaging 25ms, followed by a long period of 50ms numbers, may indeed accurately reflect a significant change in performance.

See also Alert #2 Long heartbeat.

Heartbeat time is calculated by Foxhound; it is not based on any builtin SQL Anywhere properties.

The Response... Sample time column shows how long it took for Foxhound to gather all the performance data for this sample.

Sample time should always be longer than Heartbeat time, and it will grow longer with an increasing number of connections because of the extra work involved to analyze each sample.

The Sample time is calculated after Heartbeat time and the two values do not overlap. It is possible for the Heartbeat time to be much longer than the Sample Time (e.g., 10m versus 100ms) when the target database becomes unresponsive but eventually responds; the long Heartbeat time reflects the unresponsiveness whereas the subsequent short Sample Time measures the return to normal.

Performance Tip: A long Sample Time may indicate a performance problem with Foxhound rather than the target database; e.g.:

To see where the performance problem lies, repeatedly run the following ISQL script against your target database; if this script runs quickly but Foxhound reports a large Sample Time, the problem lies with Foxhound:
SELECT * INTO #temp1 FROM rroad_engine_properties();
SELECT * INTO #temp2 FROM rroad_database_properties(1);
SELECT * INTO #temp3 FROM rroad_connection_properties();
DROP TABLE #temp1;
DROP TABLE #temp2;
DROP TABLE #temp3;

See also Alert #3 Long sample time.

Sample time is calculated by Foxhound; it is not based on any builtin SQL Anywhere properties.

The Response... Ping time column shows how long it took for Foxhound to connect and disconnect from the target database.

Performance Tip: Long Ping times may indicate that a performance bottleneck is preventing the target database from accepting new connections on a timely basis.
Ping times for local "shared memory" connections may be similar to or even smaller than Sample times for the same database, but they will usually be larger than Heartbeat times.

Ping times for network connections may be much longer than Ping times for local connections.

Foxhound uses a custom "ping" process to test separate connections to the target database.

Each time the ping process runs it opens a new connection to the target database via the embedded SQL interface, issues a SELECT @@SPID command and then immediately disconnects.

This is different from the Foxhound Monitor process which connects to the target database via ODBC and keeps that connection open while it collects multiple samples.

Note that the Foxhound ping process does not use the dbping.exe utility that ships with SQL Anywhere, nor does it use the ODBC interface that is used to gather sample data.

Also note that the separate ping process "uses up" another SQL Anywhere connection number each time it runs, which is once approximately every 10 seconds for each target database.

The new ping process can be used in three ways:

  1. As an addition to the Foxhound Monitor sampling process, the ping process tests the target database's ability to accept new connections as well as providing data for a third measure of response time: ping response time.

    See Monitor Options - Include Ping.

    See also Alert #35 Separate ping failed.

  2. As an alternative to Foxhound's sampling process, ping-only sampling may be used to check for Alert #1 Database unavailable without storing a lot of data in the Foxhound database.

    See Monitor Options - Ping-Only Sampling.

  3. As an alternative to on/off Sample Schedule settings, ping-only sampling may be specified at various times of the day.

    For example, ping-only sampling might be scheduled during the overnight hours

    • when a large connection pool is mostly idle, or

    • when a heavy load is expected and nobody much cares about performance.

    See Monitor Options - Sample Schedule 'P' characters.

Ping time is calculated by Foxhound; it is not based on any builtin SQL Anywhere properties.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Throughput... Req, Commits, Bytes
Throughput, also known as bandwidth, is a measure of how much work the database has performed:

Throughput... Req is the rate at which the server has started processing a new request or resumed processing an existing request during the preceding interval.

Performance Tip: Large Throughput... Req values may indicate that heavy client load on the database is a performance bottleneck. Small values may indicate that some other performance bottleneck is preventing the database from processing client requests.

Note that "request" is an atomic internal unit of work processed by the server for a connection, not a client-server communication request from a client application to the SQL Anywhere server.

The latter is not displayed by Foxhound; however, it is recorded by Foxhound in the sample_connection.RequestsReceived column for adhoc queries of connection-level data.

Throughput... Req is based on the server-level Req property

(note that this is different from the connection-level Throughput... Req column which is based on the connection-level ReqCountActive property)

Throughput... Commits is the approximate rate at which commit requests have been executed by all connections in the previous interval.

Performance Tip: Large Throughput... Commits values may indicate that heavy client load on the database is a performance bottleneck. Small values may indicate that some other performance bottleneck is preventing the database from processing client requests.

This number is approximate because a connection may issue a commit and disconnect between two Foxhound samples, and that commit won't be included in this total.

The total since the server started is reset to zero and accumulation starts over again when sampling is stopped and restarted. "Commits" is roughly the same as "transaction count" unless client connections issue a lot of redundant commits.

Throughput... Commits is based on the sum of the connection-level Commit property.

Foxhound does gather the database-level Commit property for target databases running on SQL Anywhere 12 and later, and the value is stored in the sample_detail."Commit" column for adhoc queries, but it is not the value displayed by Foxhound on the Monitor and other pages.

Historically speaking, the value that Foxhound does display (the sum of the connection-level Commit property) is known to be more reliable than the database-level Commit property. However, it is possible that Foxhound may not count commits performed by short-lived connections that aren't captured at all.

This and other values displayed by Foxhound are intended for performance analysis purposes, not accounting or other purposes that require absolute accuracy.

Throughput... Bytes is the rate at which data has been received by and sent by the server across the client server interface in the previous interval.

Performance Tip: Large Throughput... Bytes values may indicate that heavy client load on the database is a performance bottleneck. Small values may indicate that some other performance bottleneck is preventing the database from processing client requests.

Throughput... Bytes is displayed for target databases running on SQL Anywhere versions 7 and later. It is based on the server-level BytesReceived and BytesSent properties for target databases running on SQL Anywhere versions 7 through 12, and on the database-level BytesReceived and BytesSent properties for versions 16 and later.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Conns / Parent, Child Conns
The Conns column shows how many connections existed on a target database running on SQL Anywhere 11 or earlier, with Foxhound itself counting as 1 connection.
- or -

The Parent, Child Conns columns show how many primary (parent) and internal (child) connections existed on a target databases running on SQL Anywhere 12 or later, with Foxhound itself counting as 1 parent connection.

Performance Tip: A large Conns or Parent Conns value may indicate that heavy client load on the database is a performance bottleneck.

See also Alert #26 Connections.

Performance Tip: A large Child Conns value (up to the number of processors available) may indicate that heavy use of intra-query parallelism is a performance bottleneck.

With intra-query parallelism, multiple processors (child connections) can do work for one client connection (the parent).

A small number of individual client connections (e.g., one) may be responsible for heavy CPU usage on multiple child connections, thus preventing other client connections from getting their work done. If you suspect this is happening, try turning down the level of intra-query parallelism (for example, SET OPTION PUBLIC.MAX_QUERY_TASKS = '4' on an eight-processor computer) or turning it off altogether (SET OPTION PUBLIC.MAX_QUERY_TASKS = '1').

The parent connection count is based on the database-level ConnCount property, and the child connection count is calculated by Foxhound as the number of connections with non-zero connection-level ParentConnection property values.

Performance Tip: The sum of the Parent and Child Conns columns should match the total number of connections shown in the connections detail section at the bottom of the page, but it may differ for the following reasons:


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Executing, Idle, Waiting Conns
The Executing, Idle, Waiting Conns columns show how many connections were executing, idle or waiting, where "waiting" includes blocked connections.

Performance Tip: A large Waiting Conns value may indicate a performance bottleneck; have a look at the connection-level Current Req Status column to find the affected connections.

The database-level Executing, Idle, Waiting Conns columns are closely related to the connection-level Current Req Status value:

       Foxhound              Foxhound
    Database-Level       Connection-Level                                                     SQL Anywhere 
Executing Idle Waiting  Current Req Status           SQL Anywhere Description                 ReqStatus
----------------------  ---------------------------  ---------------------------------------  -----------------
   Yes      -     -     Executing                    The connection is executing a request.   Executing     

    -      Yes          Idle                         The connection is not currently          Idle              
                                                        processing a request.

    -       -    Yes    Waiting for thread           The connection has work to do and        Unscheduled         
                                                        is waiting for a worker thread.

    -       -    Yes    Waiting for I/O              The connection is waiting for an I/O.    BlockedIO     
      
    -       -    Yes    Waiting for shared resource  The connection is waiting for access to  BlockedContention    
                                                     shared database server data structures.

    -       -    Yes    Blocked by lock              The connection is blocked waiting        BlockedLock
                                                     for a locked row.         

    -       -    Yes    Blocked by mutex             The connection is blocked waiting        BlockedLock (1) 
                                                     for a mutex.         

    -       -    Yes    Blocked by semaphore         The connection is blocked waiting        Executing (2)         
                                                     for a semaphore.

    Note 1: Foxhound ignores the SQL Anywhere connection-level ReqStatus value 'BlockedLock' for a connection 
            blocked by a mutex on a target database running on SQL Anywhere 17.

    Note 2: Foxhound ignores the SQL Anywhere connection-level ReqStatus value 'Executing' for a connection 
            blocked by a semaphore on a target database running on SQL Anywhere 17.

Here's an analogy that doesn't prove anything but might help understanding:

Performance Tip: The sum of the Executing, Idle, Waiting Conns columns should match the sum of the Parent and Child Conns columns, but it may differ for the following reasons:

The Executing, Idle, Waiting Conns columns are displayed for target databases running on SQL Anywhere 9 and later.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Active Req, Max Req, Unsch Req
Active Req is the number of server workers that are currently handling client-side requests.
Performance Tip: Large Active Req values may indicate that heavy client load on the database is a performance bottleneck.

Performance Tip: Small Active Req values may indicate that some other performance bottleneck is preventing the database from processing client requests.

Note that "request" is an atomic internal unit of work processed by the server for a connection, not a client-server communication request from a client application to the SQL Anywhere server.

The latter is not displayed by Foxhound; however, it is recorded by Foxhound in the sample_connection.RequestsReceived column for adhoc queries of connection-level data.

Active Req is based on the server-level ActiveReq property.

Max Req is the server multiprogramming level, or the maximum number of requests that can be processed at one time (the -gn option).

Performance Tip: A Max Req value that is too small may cause the Unsch Req value to increase, in turn causing a bottleneck that increases response time and/or decreases throughput.

Performance Tip: A Max Req value that varies up and down may indicate the server is unable to correctly determine the best value.

If the computer is dedicated to running this SQL Anywhere server and no other process of importance, consider disabling the dynamic tuning of the multiprogramming level by specifying the -gna 0 and -gn options to set a fixed value. With a dedicated computer there may be no need for SQL Anywhere to perform extra work changing the multiprogramming level up and down.

Max Req is displayed for target databases running on SQL Anywhere 9 and later, and is based on the server-level Threads property for SQL Anywhere 9 and on the server-level MultiProgrammingLevel property for SQL Anywhere 10 and later.

Unsch Req (formerly called Waiting Req) shows the number of requests that were waiting to be processed.

Performance Tip: Large Unsch Req values may indicate that some performance bottleneck is preventing the database from processing its workload.
The bottleneck may simply be a Max Req value that is too low (solution: increase the server -gn option), but the problem may be harder than that; for example, if the application design results in excessive blocking and/or too many long-running requests.

See also Alert #14 Unscheduled requests.

Unsch Req is based on the server-level UnschReq property.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Locks Held, Conns Blocked, Waiting Time
Locks Held is the total number of locks held by all connections.
Performance Tip: Large numbers of Locks Held are not a problem in themselves; SQL Anywhere is perfectly capable of handling millions of locks being held at one time.
When locks become a problem is when they are held too long and cause other connections to be blocked (prevented) from doing work.

For example, when Locks Held grows large during a period of high activity (high CPU, disk), and then *remains* high for a period of low activity, that may indicate an application flaw where a COMMIT is not issued as soon as it should be.

See also Alert #25 Locks.

The Locks Held value does not include schema locks. For example, if a SELECT statement holds a schema lock that is blocking another connection from executing an ALTER TABLE statement, Locks Held may be empty even though Conns Blocked is 1.

Locks Held is displayed for target databases running on SQL Anywhere 10 and later, and is based on the database-level LockCount property.

Conns Blocked is the number of connections that are blocked.

Performance Tip: Large numbers of blocked connections may indicate a serious performance bottleneck caused by locks being held too long.
The cause may be an application that breaks this fundamental rule of transaction design:
"Never yield control of the mouse or keyboard to the end user while database locks are being held; always do a COMMIT first."

When that rule is broken a long-running transaction is often the result, with those locks preventing other users from getting their work done while the first user decides what to do (or takes a lunch break).

See also Alert #23 Blocked connections and Alert #24 Conn blocking others.

Conns Blocked is based on the connection-level BlockedOn property for target databases running on SQL Anywhere versions 5.5 through 16, and on the connection-level BlockedOn, LockObjectType and LockObjectOID properties for version 17.

Note that Foxhound calculates the database-level Conns Blocked value by summarizing data provided by SQL Anywhere at the connection level.

Waiting Time is the total time all current connections were blocked or forced to wait during the previous interval.

Performance Tip: Long waiting times may indicate a serious performance bottleneck caused a lack of resources.
The Waiting Time value is not cumulative. A obscenely large value (such as a Waiting Time of 4h in an Interval of only 13s) is possible when, for example, 1000 connections are all trying to get work done but SQL Anywhere is only able to execute a few requests at a time.

During a period of long Waiting Time values a sudden spike (for example, 3h to 6h) may occur when SQL Anywhere performs a checkpoint.

Waiting Time is displayed for target databases running on SQL Anywhere 9 and later, and is based on the sum of the connection-level ReqTimeBlockContention, ReqTimeBlockIO, ReqTimeBlockLock and ReqTimeUnscheduled properties.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
CPU
The CPU column shows two values: the percent used during the preceding interval (nn%) and the number of processors used (of n).
The CPU time values are for the target SQL Anywhere server as a whole, not an individual target database when the server is running more than one database.

The percentages are adjusted for the number of CPUs being used by SQL Anywhere.

For example, if four processors are used, and SQL Anywhere is using 100% of one processor and 0% of the other three, Foxhound will show the CPU time as 25% of 4.

Performance Tip: CPU time is most important when the value is unexpected.

Performance Tip: If you suspect that too much CPU time is being used by SQL code inside stored procedures, triggers, events and/or web services, SQL Anywhere's own "procedure profiler" is the very best way to find those bottlenecks.

See also Alert #4 CPU time and Alert #27 Connection CPU.

The CPU time and CPU count values are displayed for target databases running on SQL Anywhere version 7 and later, and are based on the server-level NumLogicalProcessorsUsed, NumProcessorsAvail, NumProcessorsMax and ProcessCPU properties.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Temp Space, Rollback Log, Uncommitted
The Temp Space column shows the total amount of temporary file space used by all the connections.
Temporary pages are used for many purposes, most often to hold intermediate results during query processing. Even if there is no temporary file, as with an in-memory no write database, temporary space is allocated and used by the engine.

Performance Tip: Large amounts of Temp Space may indicate that runaway queries are a performance bottleneck.

To find which connections are using the most temporary file space, click on the Temp Space column heading in the connection section of Foxhound Monitor or History page. That will sort the connections in decreasing order by Temp Space.

To limit the amount of temporary file space any individual connection can use on a target database running on SQL Anywhere version 10 or later, use the MAX_TEMP_SPACE option; e.g., SET OPTION PUBLIC.MAX_TEMP_SPACE = '1G';

See also Alert #21 Temp file usage and Alert #22 Conn temp file usage.

Performance Tip: The term "temporary file" is misleading and it should be renamed "temporary space" because the data may or may not reside in the actual temporary file (which may not exist at all).

Temp Space is displayed for target databases running on SQL Anywhere version 8 and later and is based on the database-level PageSize property and the sum of the connection-level TempFilePages property.

Rollback Log shows how much space in the rollback log is currently used by all the connections.

Performance Tip: A large Rollback Log value at the server level may indicate that long-running transactions are a performance bottleneck.
Look for confirmation of this in the server-level Conns Blocked column and the connection-level Transaction Time column.

See also Alert #32 Rollback log usage.

Performance Tip: The final checkpoint stage of a normal server shutdown may also take a long time while the changes recorded in a large rollback log are being reversed.

RollBack Log is based on the database-level PageSize property and the sum of the connection-level RollbackLogPages property.

Uncommitted shows how many operations have been performed by all the connections but not yet committed.

Performance Tip: A large number of Uncommitted operations at the server level may indicate that long-running transactions are a performance bottleneck.
Look for confirmation of this in the server-level Conns Blocked column and the connection-level Transaction Time column.

See also Alert #33 Uncommitted operations and Alert #34 Long uncommitted.

Performance Tip: The count of Uncommitted operations includes (and may be exactly equal to) the number of uncommitted row-level inserts, updates and deletes.

The count of Uncommitted operations may be larger than the number of INSERT, UPDATE and DELETE statements because one statement can affect many rows.

If a single row is inserted, then updated twice and finally deleted, for example, that counts as four Uncommitted operations.

If a single row matches the WHERE clause of an UPDATE statement but all of the new column values in the SET clause are the same as the current values in the row, that row is not updated and the operation is not counted as an Uncommitted operation.

A table-level schema lock obtained by a SELECT statement is not counted as an Uncommitted operation even though the lock is not cleared until a subsequent commit or rollback (and may thus be regarded as "uncommitted").

Uncommitted is based on the sum of the connection-level UncommitOp property.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Cache Panics, Low Memory, Satisfaction
Cache Panics is the number of times the target server failed to find a cache page to allocate in the previous interval.
See also Alert #29 Cache panics.

Cache Panics is displayed for target databases running on SQL Anywhere version 9 and later, and is based on the server-level CachePanics property.

Low Memory is the number of times the target server had to change a query execution plan because cache memory ran low in the previous interval.

Low Memory is displayed for target databases running on SQL Anywhere version 8 or later and is based on the database-level QueryLowMemoryStrategy property.

Cache Satisfaction is the percentage of times a database page lookup was satisfied by the cache in the previous interval.

Performance Tip: These conditions may indicate that insufficient memory in the database cache is a performance bottleneck:

Performance Tip: If the computer is dedicated to running this SQL Anywhere server and no other process of importance, consider disabling the automatic cache size tuning process by specifying the -ca 0 and -c options to set a fixed cache size. With a dedicated computer there may be no need for SQL Anywhere to perform extra work changing the cache size up and down.

Performance Tip: A long-running UNLOAD TABLE statement may result in extreme Cache Satisfaction values like 37.74%.

Cache Satisfaction is based on the server-level CacheHits and CacheRead properties for target databases running on SQL Anywhere versions 5 and 6, and on the database-level CacheHits and CacheRead properties for versions 7 and later.


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Checkpoints, Checkpoint Urgency, Recovery Urgency
Checkpoints is the number of CHECKPOINT operations that have been executed by the server in the previous interval.
Performance Tip: Checkpoint operations can be expensive. More than one checkpoint every once in a while may indicate that undesirable behavior is causing a performance bottleneck.
Generally speaking, explicit CHECKPOINT statements are not required in application programs because the server does a good job of scheduling checkpoints to minimize their impact on performance. An explicit CHECKPOINT should never be used without careful consideration, especially in a busy multi-user environment.

Checkpoints are different from commits; a commit ensures that the transaction log file is up to date whereas a checkpoint ensures that the database file is up to date. As long as commits are performed frequently, performance can be greatly improved by delaying checkpoint operations... which is what SQL Anywhere does by default.

Performance Tip: Think twice before running a database without a transaction log. Even if you don't need the log for recovery purposes, SQL Anywhere will perform a checkpoint after every commit if there's no transaction log... and that can be very bad for performance.

Checkpoints is based on the server-level Chkpt property for target databases running on SQL Anywhere versions 5 and 6, and on the database-level Chkpt property for versions 7 and later.

Checkpoint Urgency is the percentage of the SET OPTION PUBLIC.CHECKPOINT_TIME value that has elapsed since the previous checkpoint.

See also Alert #17 Checkpoint urgency.

Checkpoint Urgency is displayed for target databases running on SQL Anywhere version 7 and later, and is based on the database-level CheckpointUrgency property.

Recovery Urgency is the estimated time required to recover the database when restarting after an abnormal stoppage, expressed as a percentage of the SET OPTION PUBLIC.RECOVERY_TIME value.

Checkpoint Urgency and Recovery Urgency are used by the target server to help decide when to take a checkpoint. They both increase monotonically until a checkpoint is taken, then drop to zero.

The Recovery Urgency may exceed 100% because SQL Anywhere enforces a lower boundary on the interval between successive checkpoints. This lower bound is calculated using the checkpoint_time and recovery_time options, and the default is 2 minutes. If Recovery Urgency increases rapidly immediately after one checkpoint is taken, it may continue far beyond 100% before the next checkpoint is allowed.

See also Alert #18 Recovery urgency.

Recovery Urgency is displayed for target databases running on SQL Anywhere version 7 or later, and is based on the database-level RecoveryUrgency property.

Performance Tip: Before changing how often SQL Anywhere takes checkpoints, think twice! SQL Anywhere almost always does an excellent job of picking the right time to perform a checkpoint without your help.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Disk/Cache: Internal Index, Leaf, Table
Disk/Cache: Internal Index is the percentage ratio between the number of index internal-node pages that have been read from disk and from the cache in the previous interval.
Disk/Cache: Internal Index is displayed for target databases running on SQL Anywhere version 7 and later, and is based on the database-level DiskReadIndInt and CacheReadIndInt properties.

Disk/Cache: Leaf is the percentage ratio between the number of index leaf pages that have been read from disk and from the cache in the previous interval.

Disk/Cache: Leaf is displayed for target databases running on SQL Anywhere version 7 and later, and is based on the database-level DiskReadIndLeaf and CacheReadIndLeaf properties.

Disk/Cache: Table is the percentage ratio between the number of table pages that have been read from disk and from the cache in the previous interval.

Disk/Cache: Table is displayed for target databases running on SQL Anywhere version 7 and later, and is based on the database-level DiskReadTable and CacheReadTable properties.

The CacheReadTable counter is incremented every time SQL Anywhere tries to read a table page.

The DiskReadTable counter is incremented every time SQL Anywhere can't find the table in the cache and has to read it from disk.

Performance Tip: These conditions may indicate that insufficient memory in the database cache is a performance bottleneck.

Performance Tip: If the computer is dedicated to running this SQL Anywhere server and no other process of importance, consider disabling the automatic cache size tuning process by specifying the -ca 0 and -c options to set a fixed cache size.

With a dedicated computer there may be no need for SQL Anywhere to perform extra work changing the cache size up and down.

Performance Tip: Disk/Cache ratios that are consistently large may indicate that cache thrashing caused by a large database page size is a performance bottleneck.

A smaller database page size may allow important pages to remain in the cache longer rather than being swapped out to disk to make room for different (giant) pages.

Performance Tip: A long-running UNLOAD TABLE statement may result in extreme Disk/Cache: Internal Index, Leaf, Table values like "- / - / 99%".


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Incomplete Reads, Writes
Incomplete Reads is the current number of file reads that have been started but not yet completed.
Performance Tip: Consistently large Incomplete Reads values (greater than zero) may indicate that there is a performance bottleneck caused by the inability of the disk system to keep up with database activity.
See also Alert #15 Incomplete I/O.

Incomplete Reads is displayed for target databases running on SQL Anywhere version 17, and is based on the database-level CurrRead property.

Incomplete Writes is the current number of file writes that have been started but not yet completed.

Performance Tip: Consistently large Incomplete Writes values (greater than zero) may indicate that there is a performance bottleneck caused by the inability of the disk system to keep up with database activity.
See also Alert #15 Incomplete I/O.

Incomplete Writes is displayed for target databases running on SQL Anywhere version 17, and is based on the database-level CurrWrite property.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Disk Reads, Disk Writes, Log Writes
Disk Reads is the number of pages that have been read from disk in the previous interval.
Disk Reads is based on the server-level DiskRead property for target databases running on SQL Anywhere versions 5 and 6, and on the database-level DiskRead property for versions 7 and later.

Disk Writes is the number of modified pages that have been written to disk in the previous interval.

Disk Writes is based on the server-level DiskWrite property for target databases running on SQL Anywhere versions 5 and 6, and on the database-level DiskWrite property for versions 7 and later.

Log Writes column shows the number of pages that have been written to the transaction log in the previous interval.

Log Writes is based on the server-level LogWrite property for target databases running on SQL Anywhere versions 5 and 6, and on the database-level LogWrite property for versions 7 and later.

Performance Tip: Large Disk Reads, Disk Writes, Log Writes values may indicate that heavy disk I/O is a performance bottleneck.

See also Alert #16 I/O operations.

Performance Tip: Disk Reads and Disk Writes count page-level input and output operations on the SYSTEM, temporary and secondary dbspace files, and Log Writes counts pages written to the transaction log file. Other files are excluded; e.g., non-dbspace files used by LOAD and UNLOAD statements and by xp_read_file() and xp_write_file() procedure calls.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Index Adds, Lookups, Satisfaction
Index Adds is the number of times an entry has been added to an index in the previous interval.

Performance Tip: A large Index Adds value may indicate that a large number of row inserts is a performance bottleneck ...or a large number of row updates that are changing index columns.

Index Adds is based on the server-level IndAdd property for target databases running on SQL Anywhere versions 5.5 and 6, and on the database-level IndAdd property for target databases running on SQL Anywhere versions 7 and later.

Index Lookups is the number of times an entry has been looked up in an index in the previous interval.

Performance Tip: A large Index Lookups value may indicate that heavy index usage is a performance bottleneck ...or just the opposite; heavy index usage is often better than the alternative (frequent retrieval of data pages).

Index Lookups is based on the server-level IndLookup property for target databases running on SQL Anywhere versions 5.5 and 6, and on the database-level IndLookup property for target databases running on SQL Anywhere versions 7 and later.

Index Satisfaction is the percentage of times that an index lookup was satisfied by the index without having to retrieve more information from the table data in the previous interval.

Performance Tip: Small Index Satisfaction values (less than 100%) may indicate that low index selectivity is causing a performance bottleneck.
Index selectivity is the ability to locate individual entries within index pages without having to read table pages.

When index selectivity is low it often means

  • SQL Anywhere has chosen the wrong index for a particular query predicate (a rare event but possible),

  • the index design is inadequate for the task of satisfying that query predicate (more likely), and/or

  • the index is fragmented (also possible; see the sa_index_levels() procedure).

To increase Index Satisfaction at the database level it may be necessary to find the individual queries that are responsible; try clicking on the connection section column titles Full Index Comps or Index Satisfaction to sort the connections in descending order.

When you find the responsible queries, use SQL Anywhere's Graphical Plan With Statistics feature to examine index choice and usage.

Note: Index Satisfaction is different from Cache Satisfaction; one compares index and table usage, the other compares memory and disk.

Index Satisfaction is based on the server-level IndLookup and FullCompare properties for target databases running on SQL Anywhere versions 5.5 and 6, and on the database-level IndLookup and FullCompare properties for target databases running on SQL Anywhere versions 7 and later.


Foxhound 4 5. The Connection History Page 5.2 Top Sample 
Full Index Comps
Full Index Comps shows how many times additional information had to be obtained from the table data in order to satisfy an index lookup in the previous interval.

Performance Tip: Large values of Full Index Comps may indicate that low index selectivity is causing a performance bottleneck.

Index selectivity is the ability to locate individual entries within index pages without having to read table pages.

When index selectivity is low it often means

To reduce the number of Full Index Comps at the database level it may be necessary to find the individual queries that are responsible; try clicking on the connection section column titles Full Index Comps or Index Satisfaction to sort the connections in descending order.

When you find the responsible queries, use SQL Anywhere's Graphical Plan With Statistics feature to examine index choice and usage.

Full Index Comps is based on the server-level FullCompare property for target databases running on SQL Anywhere versions 5.5 and 6, and on the database-level FullCompare property for target databases running on SQL Anywhere versions 7 and later.


Foxhound 4 5. The Connection History Page 
5.3 Connection Identification

The Connection Identification section displays the values that uniquely identify this connection apart from all other connections that exist now, or have ever existed, or will ever exist on any target database recorded by this copy of Foxhound.

Conn #, User, OS User, IP, Name

Login Time

Connection Id String

Parent Conn #, User, OS User, IP, Name


Foxhound 4 5. The Connection History Page 5.3 Connection Identification 
Conn #, User, OS User, IP, Name
The Conn #, User, OS User, IP, Name columns identify this connection.

Conn # is the connection number of the connection.

SQL Anywhere assigns a unique connection number to each connection started since the database started. Recent versions of SQL Anywhere assign small numbers (1, 2, 3, ...) to external client connections, and large numbers to events, web services and internal ("temporary") connections (1000000065, 1000000066, ...).
The range for external client connection numbers is 1 through 999,999,999. If that range is exceeded the numbering starts at 1 again, but numbers already in use are skipped.

There will never be two connections with the same number until the SQL Anywhere server is stopped and restarted.

Two numbers may be shown in the Conn # column for temporary internal or "child" connections that have been started by some other "parent" connection.

In this case, the first number will be the parent connection number and the second number will be the actual connection number for the internal connection; e.g., 1 1000000090
Conn #, User, OS User, IP, Name
1 / DBA / Breck / - / ddd16-1
1 1000000090 / - / - / - / INT: Exchange
1 1000000091 / - / - / - / INT: Exchange
1 1000000092 / - / - / - / INT: Exchange
1 1000000093 / - / - / - / INT: Exchange
1 1000000094 / - / - / - / INT: Exchange
1 1000000095 / - / - / - / INT: Exchange
1 1000000096 / - / - / - / INT: Exchange
1 1000000097 / - / - / - / INT: Exchange

The Conn # column contains a single number for target databases running on SQL Anywhere 5.5 through 11, and one or two numbers for target databases running on SQL Anywhere 12 and later.

When the Conn # contains a single number, it is based on the connection-level Number property.

When the Conn # contains a two numbers, the first number is based on the connection-level ParentConnection property and the second number is based on the connection-level Number property.

User is the SQL Anywhere database user id that was used to make the connection; e.g., DBA.

User is based on the connection-level Userid property.

OS User is the operating system user id associated with the client process.

When the OS User is available, it may be easier to use for administrative purposes than the SQL Anywhere user id or the IP address; e.g., when identifying individual users and/or contacting them when connections are dropped.

OS User is displayed for target databases running on SQL Anywhere version 11 and later and is based on the connection-level OSUser property.

IP is the network IP address of the client side of the connection; e.g., 192.168.1.104.

IP is based on the connection-level NodeAddress property.

Name is the connection name of the connection.

Performance Tip: Try using the ConnectionName (CON=) parameter to uniquely identify the actual end user responsible for each client connection.
This is sometimes helpful when it's too hard to figure out who's doing what by looking at the User, OS User or IP values in Foxhound output.

Connection names may be automatically assigned as follows:

Name is based on the connection-level Name property.


Foxhound 4 5. The Connection History Page 5.3 Connection Identification 
Login Time
The Login Time column helps to uniquely identify this connection apart from earlier or later connections which may have the same connection number because the target server was restarted.

Login Time is displayed for target databases running on SQL Anywhere 9 and later, and is based on the connection-level LoginTime property.


Foxhound 4 5. The Connection History Page 5.3 Connection Identification 
Connection Id String
The Connection Id String column is an artificial identifier constructed by Foxhound to uniquely identify each target connection within the entire Foxhound database.

Foxhound uses this string to create URLs for opening new Connection History pages. You may find it useful when creating adhoc queries to select all the history for one connection. It is stored in the sample_connection.connection_id_string column, and there is an index on that column.

Here's the format of the Connection Id String:

ss-cc-yyyymmddhhnnss-sss
where...
ss                   sample_connection.sampling_id - unique identifier to each target database sampling session
cc                   sample_connection.connection_number  
yyyymmddhhmmss-sss   DATEFORMAT ( sample_connection.LoginTime, 'YYYYMMDDHHNNSS-SSS' ) 

Note: It is possible for two or more different Connection Id String values to represent the same actual connection. This can happen if you accidentally create two or more separate Foxhound sampling sessions for the same target database; e.g., by using a DSN and a Connection String that point to the same target database. The result will be two or more sets of data about the same connection, using different values in the sampling_id column. This is not a fatal error, simply a waste of Foxhound resources, and it shouldn't affect your adhoc queries; it is still true that a single Connection Id String value will uniquely identify a single actual connection.

Connection Id String is available for target databases running on SQL Anywhere 9 and later.


Foxhound 4 5. The Connection History Page 5.3 Connection Identification 
Parent Conn #, User, OS User, IP, Name
The Parent Conn #, User, OS User, IP, Name columns are displayed when the current connection is a child connection, and they form a link that opens a separate Connection History page for the parent connection to this child connection.
Conn #, User, OS User, IP, Name             ...   Parent Conn #, User, OS User, IP, Name
3 1000008782 / - / - / - / INT: Exchange          3 / DBA / Breck / - / ddd16-1

Parent Conn #, User, OS User, IP, Name is displayed for target databases running on SQL Anywhere 12 and later, and is based on the connection-level ParentConnection property.


Foxhound 4 5. The Connection History Page 
5.4 Connection Samples

The Connection Samples section shows performance statistics for a single connection over time.

Connection Samples Section

[9,9999]

Hide Details / Show Details

Connection Samples Column

Interval

Time Connected

Throughput... Req, Commits, Bytes

Locks Held, Conns Blocked, Transaction Time

Waiting Time, Busy, Wait, Idle

CPU, Child Conns

Temp Space, Rollback Log, Uncommitted

Low Memory, Cache Satisfaction

Time Since Last Request

Current Req Status

Disk/Cache: Internal Index, Leaf, Table

Disk Reads, Disk Writes, Log Writes

Index Adds, Lookups, Satisfaction

Full Index Comps

Isolation Level

AutoDropped for this reason:

Autodrop Result:

Blocked By:

Block Reason:

Locked Row Query:

Last Statement:

Last Plan Text:


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
[9,9999]
The pair of numbers [in square brackets] above the "Connection Samples" column title are Foxhound database primary key values that can be used when coding adhoc queries; e.g., [4,1796].

The first number is the sampling_id which identifies the Foxhound Monitor session for this target database.

The meaning of the second number depends on the type of data displayed in the top row of this section; for example:

SELECT * FROM alert                   WHERE alert_occurrence           = 1796;
SELECT * FROM alert_cancelled         WHERE alert_cancelled_occurrence = 1796;
SELECT * FROM all_clear               WHERE all_clear_occurrence       = 1796;
SELECT * FROM autodropped_connection  WHERE autodrop_occurrence        = 1796;
SELECT * FROM email_failure           WHERE email_failure_occurrence   = 1796;
SELECT * FROM sample_connection       WHERE sample_set_number          = 1796;

Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Hide Details / Show Details
The Hide Details / Show Details buttons alternate between hiding and displaying the following lines for each connection:

Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Connection Samples
The Connection Samples column shows the date/time that Foxhound recorded each sample.
You can click on the History link to open a new Sample History page in a separate browser window or tab, scrolled to the associated sample.

You can click on the date/time link to scroll the current Connection History page to the associated sample.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Interval
The Interval column shows the actual time interval between the previous sample and this one.
Foxhound tries to record a new sample every 10 seconds but the actual interval can vary.

Foxhound uses the interval time to convert performance statistics from cumulative counts to rates; e.g., to convert the total number of disk writes into the number of disk writes per second.

A very long interval like 1h 19.8m may indicate the computer was in sleep, standby or hibernate mode.

See also Alert #1 Database unresponsive.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Time Connected
Time Connected is the elapsed time between the time this connection was established and the sample time.
Time Connected is displayed for target databases running on SQL Anywhere 9 and later, and is based on the connection-level LoginTime property.

Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Throughput... Req, Commits, Bytes
Throughput, also known as bandwidth, is a measure of how much work the database has performed:

Throughput... Req is the rate at which the server has started processing a new request or resumed processing an existing request for this connection in the previous interval.

Performance Tip: Large Throughput... Req values may indicate that this connection is placing a heavy load on the database.

Note that "request" is an atomic internal unit of work processed by the server for a connection, not a client-server communication request from a client application to the SQL Anywhere server.

The latter is not displayed by Foxhound; however, it is recorded by Foxhound in the sample_connection.RequestsReceived column for adhoc queries of connection-level data.

Throughput... Req is displayed for target databases running on SQL Anywhere version 9 and later, and is based on the connection-level ReqCountActive property.

(note that this is different from the server-level Throughput... Req column which is based on the server-level Req property)

Throughput... Commits is the rate at which commit requests have been handled by the server for this connection in the previous interval.

Performance Tip: Large Throughput... Commits values may indicate that this connection is placing a heavy load on the database.

Throughput... Commits is based on the connection-level Commit property.

Throughput... Bytes is the rate at which data has been received by and sent by the server across the client server interface for this connection in the previous interval.

Performance Tip: Large Throughput... Bytes values may indicate that this connection is placing a heavy load on the database.

Throughput... Bytes is displayed for target databases running on SQL Anywhere versions 8 and later, and is based on the connection-level BytesReceived and BytesSent properties.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Locks Held, Conns Blocked, Transaction Time
Locks Held is the total number of locks held by this connection.
Performance Tip: Large numbers of Locks Held are not a problem in themselves; SQL Anywhere is perfectly capable of handling millions of locks being held at one time.
When locks become a problem is when they are held too long and cause other connections to be blocked (prevented) from doing work.

For example, when Locks Held grows large during a period of high activity (high CPU, disk), and then *remains* high for a period of low activity, that may indicate an application flaw where a COMMIT is not issued as soon as it should be.

See also Alert #25 Locks.

The Locks Held value does not include schema locks. For example, if a SELECT statement holds a schema lock that is blocking another connection from executing an ALTER TABLE statement, Locks Held may be empty even though Conns Blocked is 1.

Locks Held is displayed for target databases running on SQL Anywhere 10 and later, and is based on the connection-level LockCount property.

Conns Blocked is the number of other connections that were blocked by this connection.

Performance Tip: Large numbers of blocked connections may indicate a serious performance bottleneck caused by locks being held too long.
The cause may be an application that breaks this fundamental rule of transaction design:
"Never yield control of the mouse or keyboard to the end user while database locks are being held; always do a COMMIT first."

When that rule is broken a long-running transaction is often the result, with those locks preventing other users from getting their work done while the first user decides what to do (or takes a lunch break).

See also Alert #23 Blocked connections and Alert #24 Conn blocking others.

Conns Blocked is based on the connection-level BlockedOn property for target databases running on SQL Anywhere versions 5.5 through 16, and on the connection-level BlockedOn, LockObjectType and LockObjectOID properties for target databases running on SQL Anywhere 17.

Transaction Time is the length of time since the database was first modified by this connection after a COMMIT or ROLLBACK.

Performance Tip: A long Transaction Time may indicate that a long-running transaction is a performance bottleneck.
Note that while it is possible for a SELECT to acquire locks and thus block other connections (e.g., a shared lock obtained by a SELECT will block an ALTER TABLE), a SELECT does not count as a modification as far as the Transaction Time is concerned. In other words, a SELECT does not start a transaction.

See also Alert #28 Long transaction.

Transaction Time is displayed for target databases running on SQL Anywhere 8 and later, and is based on the connection-level TransactionStartTime property.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Waiting Time, Busy, Wait, Idle

Waiting Time is the total amount of time this connection has been blocked or forced to wait.

Performance Tip: Long waiting times may indicate a serious performance bottleneck caused a lack of resources.

Waiting Time is displayed for target databases running on SQL Anywhere 9 and later, and is based on the sum of the connection-level ReqTimeBlockContention, ReqTimeBlockIO, ReqTimeBlockLock and ReqTimeUnscheduled properties.

The Busy, Wait, Idle columns are intended to give the user a rough idea of what's going on at the connection level. They are displayed as cumulative percentages since login:

The Busy, Wait, Idle columns are displayed for target databases running on SQL Anywhere 9 and later, and are based on the connection-level LoginTime, ReqTimeActive, ReqTimeBlockContention, ReqTimeBlockIO, ReqTimeBlockLock and ReqTimeUnscheduled properties:

   total_time = time since LoginTime
   busy_time  = ReqTimeActive - ReqTimeBlockIO - ReqTimeBlockContention - ReqTimeBlockLock
   wait_time  = ReqTimeUnscheduled + ReqTimeBlockIO + ReqTimeBlockContention + ReqTimeBlockLock 
   idle_time  = total_time - busy_time - wait_time


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
CPU, Child Conns
The CPU column shows how much of the overall CPU time available was used by this connection in the previous interval. The percentage is adjusted for the number of CPUs being used by the server.

See also Alert #4 CPU time and Alert #27 Connection CPU.

The CPU % is displayed for target databases running on SQL Anywhere 10 and later, and is based on the connection-level ApproximateCPUTime property and the server-level NumLogicalProcessorsUsed property.

The Child Conns column displays the number of internal child connections that have been started by each primary parent connection.

When a connection makes use of the intra-query parallelism feature, it spawns a number of internal child connections which do most of the work; e.g., one INT: EXCHANGE child connection for each available processor.

Performance Tip: Some versions of SQL Anywhere report the total CPU time used by all the child connections as the ApproximateCPUTime value for each child connection in use, and almost none for the parent connection. This inflates the amount of CPU time used by each child connection without reporting any CPU usage by the parent connection.

In an attempt to make sense of this behavior, Foxhound calculates the average non-zero ApproximateCPUTime for the child connections and reports it as the CPU time for this parent connection. The inflated values reported by SQL Anywhere for each child connection are still shown by Foxhound; only the parent connection CPU time is adjusted.

One consequence of the Foxhound calculations is that the AutoDrop #5 CPU Usage process does apply to parent connections using intra-query parallelism. Note that the AutoDrop process is never performed on a child connection or any other internal connection that isn't directly associated with a client application.

Child Conns is displayed for target databases running on SQL Anywhere 12 and later, and is based on the connection-level ParentConnection property.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Temp Space, Rollback Log, Uncommitted
Temp Space shows how much temporary space is currently used by this connection.
Temporary pages are used for many purposes, most often to hold intermediate results during query processing. Even if there is no temporary file, as with an in-memory no write database, temporary space is allocated and used by the engine.

Performance Tip: Large amounts of Temp Space may indicate that runaway queries are a performance bottleneck.

To find which connections are using the most temporary file space, click on the Temp Space column heading in the connection section of Foxhound Monitor or History page. That will sort the connections in decreasing order by Temp Space.

To limit the amount of temporary file space any individual connection can use on a target database running on SQL Anywhere version 10 or later, use the MAX_TEMP_SPACE option; e.g., SET OPTION PUBLIC.MAX_TEMP_SPACE = '1G';

See also Alert #21 Temp file usage and Alert #22 Conn temp file usage.

Performance Tip: The term "temporary file" is misleading and it should be renamed "temporary space" because the data may or may not reside in the actual temporary file (which may not exist at all).

Temp Space is displayed for target databases running on SQL Anywhere version 8 and later, and is based on the database-level PageSize property and the connection-level TempFilePages property.

Rollback Log shows how much space in the rollback log is currently used by this connection.

Performance Tip: A large Rollback Log value at the connection level may indicate that a long-running transaction is a performance bottleneck.
Look for confirmation of this in the connection-level Conns Blocked and Transaction Time columns.

See also Alert #32 Rollback log usage.

Performance Tip: The final checkpoint stage of a normal server shutdown may also take a long time while the changes recorded in a large rollback log are being reversed.

RollBack Log is based on the database-level PageSize property and the connection-level RollbackLogPages property.

Uncommitted shows how many operations have been performed by this connection but not yet committed.

Performance Tip: A large number of Uncommitted operations at the connection level may indicate that a long-running transaction is a performance bottleneck.
Look for confirmation of this in the connection-level Conns Blocked and Transaction Time columns.

See also Alert #33 Uncommitted operations and Alert #34 Long uncommitted.

Performance Tip: The count of Uncommitted operations includes (and may be exactly equal to) the number of uncommitted row-level inserts, updates and deletes.

The count of Uncommitted operations may be larger than the number of INSERT, UPDATE and DELETE statements because one statement can affect many rows.

If a single row is inserted, then updated twice and finally deleted, for example, that counts as four Uncommitted operations.

If a single row matches the WHERE clause of an UPDATE statement but all of the new column values in the SET clause are the same as the current values in the row, that row is not updated and the operation is not counted as an Uncommitted operation.

A table-level schema lock obtained by a SELECT statement is not counted as an Uncommitted operation even though the lock is not cleared until a subsequent commit or rollback (and may thus be regarded as "uncommitted").

Uncommitted is based on the connection-level UncommitOp property.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Low Memory, Cache Satisfaction
Low Memory is the number of times since this connection started that the target server had to change a query execution plan for this connection because cache memory ran low.
Low Memory is displayed for target databases running on SQL Anywhere version 8 or later and is based on the connection-level QueryLowMemoryStrategy property.

Cache Satisfaction is the percentage of times since this connection started that a database page lookup for this connection was satisfied by the cache.

Performance Tip: These conditions may indicate that insufficient memory in the database cache is a performance bottleneck:

Performance Tip: If the computer is dedicated to running this SQL Anywhere server and no other process of importance, consider disabling the automatic cache size tuning process by specifying the -ca 0 and -c options to set a fixed cache size. With a dedicated computer there may be no need for SQL Anywhere to perform extra work changing the cache size up and down.

Performance Tip: A long-running UNLOAD TABLE statement may result in extreme Cache Satisfaction values like 37.74%.

Cache Satisfaction is displayed for target databases running on SQL Anywhere 8 and later, and is based on the connection-level CacheHits and CacheRead properties.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Time Since Last Request
Time Since Last Request is the elapsed time since the last time a request was started for this connection.
Performance Tip: If this connection is blocked, Time Since Last Request tells you exactly how long it has been waiting.

Performance Tip: A long Time Since Last Request is usually associated with an idle connection, but if the connection is busy (high CPU, high disk activity, etc.) it could mean that some single operation is "stuck" using up resources but not getting anywhere.

Time Since Last Request is based on the connection-level LastReqTime property.


[Top of Section
Current Req Status
Current Req Status shows whether this connection was Idle, Waiting, Blocked or Executing.

Performance Tip: A blocked or waiting connection is a dramatic form of performance bottleneck when it corresponds to an end user who is unable get any work done.

The connection-level Current Req Status is closely related to the database-level Executing, Idle, Waiting Conns columns:

       Foxhound              Foxhound
    Database-Level       Connection-Level                                                     SQL Anywhere 
Executing Idle Waiting  Current Req Status           SQL Anywhere Description                 ReqStatus
----------------------  ---------------------------  ---------------------------------------  -----------------
   Yes      -     -     Executing                    The connection is executing a request.   Executing     

    -      Yes          Idle                         The connection is not currently          Idle              
                                                        processing a request.

    -       -    Yes    Waiting for thread           The connection has work to do and        Unscheduled         
                                                        is waiting for a worker thread.

    -       -    Yes    Waiting for I/O              The connection is waiting for an I/O.    BlockedIO     
      
    -       -    Yes    Waiting for shared resource  The connection is waiting for access to  BlockedContention    
                                                     shared database server data structures.

    -       -    Yes    Blocked by lock              The connection is blocked waiting        BlockedLock
                                                     for a locked row.         

    -       -    Yes    Blocked by mutex             The connection is blocked waiting        BlockedLock (1) 
                                                     for a mutex.         

    -       -    Yes    Blocked by semaphore         The connection is blocked waiting        Executing (2)         
                                                     for a semaphore.

    Note 1: Foxhound ignores the SQL Anywhere connection-level ReqStatus value 'BlockedLock' for a connection 
            blocked by a mutex on a target database running on SQL Anywhere 17.

    Note 2: Foxhound ignores the SQL Anywhere connection-level ReqStatus value 'Executing' for a connection 
            blocked by a semaphore on a target database running on SQL Anywhere 17.

Here's an analogy that doesn't prove anything but might help understanding:

Current Req Status is displayed for target databases running on SQL Anywhere 9 and later.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Disk/Cache: Internal Index, Leaf, Table
Disk/Cache: Internal Index is the percentage ratio between the number of index internal-node pages that have been read from disk and from the cache for this connection in the previous interval.
Disk/Cache: Internal Index is displayed for target databases running on SQL Anywhere version 7 and later, and is based on the connection-level DiskReadIndInt and CacheReadIndInt properties.

Disk/Cache: Leaf is the percentage ratio between the number of index leaf pages that have been read from disk and from the cache for this connection in the previous interval.

Disk/Cache: Leaf is displayed for target databases running on SQL Anywhere version 7 and later, and is based on the connection-level DiskReadIndLeaf and CacheReadIndLeaf properties.

Disk/Cache: Table is the percentage ratio between the number of table pages that have been read from disk and from the cache for this connection in the previous interval.

Disk/Cache: Table is displayed for target databases running on SQL Anywhere version 7 and later, and is based on the connection-level DiskReadTable and CacheReadTable properties.

The CacheReadTable counter is incremented every time SQL Anywhere tries to read a table page.

The DiskReadTable counter is incremented every time SQL Anywhere can't find the table in the cache and has to read it from disk.

Performance Tip: These conditions may indicate that insufficient memory in the database cache is a performance bottleneck.

Performance Tip: If the computer is dedicated to running this SQL Anywhere server and no other process of importance, consider disabling the automatic cache size tuning process by specifying the -ca 0 and -c options to set a fixed cache size.

With a dedicated computer there may be no need for SQL Anywhere to perform extra work changing the cache size up and down.

Performance Tip: Disk/Cache ratios that are consistently large may indicate that cache thrashing caused by a large database page size is a performance bottleneck.

A smaller database page size may allow important pages to remain in the cache longer rather than being swapped out to disk to make room for different (giant) pages.

Performance Tip: A long-running UNLOAD TABLE statement may result in extreme Disk/Cache: Internal Index, Leaf, Table values like "- / - / 99%".


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Disk Reads, Disk Writes, Log Writes
Disk Reads is the rate at which pages were read from disk for this connection in the previous interval.
Disk Reads is based on the connection-level DiskRead property..

Disk Writes is the rate at which modified pages were written to disk for this connection in the previous interval.

Disk Writes is based on the connection-level DiskWrite property..

Log Writes is the rate at which pages were written to the transaction log for this connection in the previous interval.

Log Writes is based on the connection-level LogWrite property.

Performance Tip: Large Disk Reads, Disk Writes, Log Writes values may indicate that heavy disk I/O is a performance bottleneck.

See also Alert #16 I/O operations.

Performance Tip: Disk Reads and Disk Writes count page-level input and output operations on the SYSTEM, temporary and secondary dbspace files, and Log Writes counts pages written to the transaction log file. Other files are excluded; e.g., non-dbspace files used by LOAD and UNLOAD statements and by xp_read_file() and xp_write_file() procedure calls.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Index Adds, Lookups, Satisfaction
Index Adds is the rate at which entries were added to indexes for this connection in the previous interval.
Performance Tip: A large Index Adds value may indicate that a large number of row inserts is a performance bottleneck ...or a large number of row updates that are changing index columns.

Index Adds is based on the connection-level IndAdd property.

Index Lookups is the rate at which entries were looked up in indexes for this connection in the previous interval.

Performance Tip: A large Index Lookups value may indicate that heavy index usage is a performance bottleneck ...or just the opposite; heavy index usage is often better than the alternative (frequent retrieval of data pages).

Index Lookups is based on the connection-level IndLookup property.

Index Satisfaction is the percentage of times that an index lookup was satisfied by the index without having to retrieve more information from the table data, for this connection since it started. Index Adds is the rate at which entries were added to indexes for this connection in the previous interval.

Performance Tip: Small Index Satisfaction values (less than 100%) may indicate that low index selectivity is causing a performance bottleneck.
Index selectivity is the ability to locate individual entries within index pages without having to read table pages.

When index selectivity is low it often means

  • SQL Anywhere has chosen the wrong index for a particular query predicate (a rare event but possible),

  • the index design is inadequate for the task of satisfying that query predicate (more likely), and/or

  • the index is fragmented (also possible; see the sa_index_levels() procedure).

To reduce the number of Full Index Comps, determine the SQL query that was running and then use SQL Anywhere's Graphical Plan With Statistics feature to examine index choice and usage.

Note: Index Satisfaction is different from Cache Satisfaction; one compares index and table usage, the other compares memory and disk.

Index Satisfaction is based on the connection-level IndLookup and FullCompare properties.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Full Index Comps
Full Index Comps is the rate at which additional information had to be obtained from the table data in order to satisfy an index lookup, for this connection in the previous interval.

Performance Tip: Large values of Full Index Comps may indicate that low index selectivity is causing a performance bottleneck.

Index selectivity is the ability to locate individual entries within index pages without having to read table pages.

When index selectivity is low it often means

To reduce the number of Full Index Comps, determine the SQL query that was running and then use SQL Anywhere's Graphical Plan With Statistics feature to examine index choice and usage.

Full Index Comps is based on the connection-level FullCompare property.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Isolation Level
Isolation Level shows the current isolation level and the updatable statement snapshot isolation level settings for this connection:

Performance Tip: Large values of Full Index Comps may indicate that low index selectivity is causing a performance bottleneck.

Index selectivity is the ability to locate individual entries within index pages without having to read table pages.

When index selectivity is low it often means

  • SQL Anywhere has chosen the wrong index for a particular query predicate (a rare event but possible),

  • the index design is inadequate for the task of satisfying that query predicate (more likely), and/or

  • the index is fragmented (also possible; see the sa_index_levels() procedure).

To reduce the number of Full Index Comps, determine the SQL query that was running and then use SQL Anywhere's Graphical Plan With Statistics feature to examine index choice and usage.

Full Index Comps is based on the connection-level FullCompare property.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
AutoDropped for this reason:
If this connection has been has been dropped by Foxhound's AutoDrop process, an AutoDropped for this reason: message will appear with an explanation; e.g.:
AutoDropped for this reason: #1: This connection has been blocking 1 or more (currently 1) 
   other connections for 5 or more (currently 5) samples

Note that a dropped connection may keep running for a while as SQL Anywhere rolls back its work even though the client application has been disconnected.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Autodrop Result:
If Foxhound's AutoDrop process dropped or attempted to drop a connection, the Autodrop Result: line will explain whether the attempt was successful or not; e.g.:
Autodrop Result: OK... issued at 2013-12-26 14:35:28.326, processed at 2013-12-26 14:35:28.345

AutoDrop Result: Failed... issued at 2014-02-07 16:30:06.090, failed at 2014-02-07 16:30:06.114: SQLCODE = -660, 
                 SQLSTATE = WO005, ERRORMSG() = Server 'p001': [Sybase][ODBC Driver][SQL Anywhere]
                 Permission denied: you do not have permission to disconnect "29"

Note that a dropped connection may keep running for a while as SQL Anywhere rolls back its work even though the client application has been disconnected.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Blocked By:
The Blocked By: Conn #, User, OS User, IP, Name line identifies the connection that is blocking this one.

Performance Tip: If the target database is running on SQL Anywhere Version 9 or later, the Blocked By: Conn #, User, OS User, IP, Name columns form a link that opens the Connection History page in a separate browser window or tab. That page will show just this one single connection over time.

See also Alert #23 Blocked connections and Alert #24 Conn blocking others.

Blocked By: Conn # is the connection number of the blocking connection.

Blocked By: Conn # is based on the connection-level BlockedOn property.

Blocked By: User is the SQL Anywhere database user id that was used to make the connection; e.g., DBA.

Blocked By: User is based on the connection-level Userid property.

Blocked By: OS User is the operating system user id associated with the blocking client process.

Blocked By: OS User is displayed for target databases running on SQL Anywhere version 11 and later and is based on the connection-level OSUser property.

Blocked By: IP is the network IP address of the client side of the blocking connection; e.g., 192.168.1.104.

Blocked By: IP is based on the connection-level NodeAddress property.

Blocked By: Name is the connection name of the blocking connection.

Blocked By: Name is based on the connection-level Name property.

Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Block Reason:
The Block Reason: line describes the lock that's blocking the connection; e.g.:
Block Reason: Row Transaction Write lock on DBA.t

Block Reason: Row Transaction Intent, Row Transaction Write, Row Transaction WriteNoPK lock on dba.t

Block Reason: Mutex Connection Exclusive lock on dba.test_mutex

Block Reason: Semaphore Connection lock on dba.test_semaphore

The format of Block Reason: depends on the level of detail provided to Foxhound by the target database; for example, only SQL Anywhere 17 supports Mutex and Semaphore locks.

Here are the various layouts used, from high to low levels of detail:

Block Reason: [class] [scope/duration] [type] lock on [owner].[object]
              [class] [scope/duration] [type] lock on [object]
              [class] [scope/duration] [type] 
              Lock on [owner].[object]
              Lock on [object]

                  Fields...
         [class]: Schema, Row, Table, Position, Mutex, Semaphore
[scope/duration]: Transaction, Position, Connection   
          [type]: Shared, Exclusive, Write, ...
         [owner]: object creator
        [object]: table, mutex or semaphore name

Block Reason is based on the sa_locks() procedure, the SYSMUTEXSEMAPHORE table, and the connection-level BlockedOn, LockObjectType and LockObjectOID properties.

See also Alert #23 Blocked connections and Alert #24 Conn blocking others.

Block Reason is displayed for target databases running on SQL Anywhere 7 and later, and is based on


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Locked Row Query:
The Locked Row Query: line displays a SELECT statement you can copy and paste into dbisql to find the row in the target database that is locked; e.g.,
Locked Row Query: SELECT * FROM DBA.t WHERE ROWID ( t ) = 37814272;

See also Alert #23 Blocked connections and Alert #24 Conn blocking others.

Locked Row Query is displayed for target databases running on SQL Anywhere 10 and later, and is based on the sa_locks() procedure.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Last Statement:
The Last Statement: line displays the last SQL statement received from the client application on this connection, as of the point this sample was recorded:
Last Statement: [Show More] select "COUNT_BIG"() -- 14 seconds from "SYSTAB" as "A" cross join "SYSTABCOL" as "B" c...

If the value is too long to show on one line, click on [Show More]:

Last Statement: [Show Less] 
                select "COUNT_BIG"() -- 14 seconds
                  from "SYSTAB" as "A"
                    cross join "SYSTABCOL" as "B"
                    cross join "SYSUSER" as "C"

Last Statement is displayed for target databases running on SQL Anywhere 8 and later, and is based on the connection-level LastStatement property.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples 
Last Plan Text:
The Last Plan Text: line displays the last query execution plan used by this connection, as of the point this sample was recorded:
Last Plan Text: [Show More] ( Plan ( SingleRowGroupBy ( Exchange [ 8 ] ( SingleRowGroupBy ( Nested...

If the value is too long to show on one line, click on [Show More]:

Last Plan Text: [Show Less] 
                ( Plan 
                ( SingleRowGroupBy 
                    ( Exchange [ 8 ]
                      ( SingleRowGroupBy 
                        ( NestedLoopsJoin
                          ( NestedLoopsJoin
                            ( ParallelTableScan ( ISYSUSER su ) )
                            ( TableScan ( ISYSTAB tab ) )
                          )
                          ( TableScan ( ISYSTABCOL col ) )
                        )
                      )
                    )
                  )
                )

Last Plan Text is displayed for target databases running on SQL Anywhere 10 and later, and is based on the connection-level LastPlanText property.


Foxhound 4 5. The Connection History Page 5.4 Connection Samples