tune - connect_cdc_sqdata

The tune command is intended advanced performance tuning and diagnostic performance testing only. It should only be used under the direct guidance of Precisely Support or Professional Services. The diagnostic parameters my generate Very High volume of output in a production environment.

Parameters are specific to particular Capture and Publisher agents and dynamically enabled and disabled. They are "applied" immediately unlike most SQDCONF parameters that require the Stop/Apply/Start sequence. If not disabled the parameters will persists until the agent is unmounted.

Syntax

sqdconf tune <cab_file_name>
[--enable-ack-trace |--disable-ack-trace]
[--enable-throttle |--disable-throttle]
[--enable-uow-tracker | --disable-uow-tracker]
[--uow-tracker-threshold=<uow_operations>]

Parameters and Descriptions

Parameter	Description
[--enable-ack-trace \|--disable-ack-trace]	Turn on/off diagnostic acknowledgment (ACK) latency (the ACK receive time minus the commit time) trace for Db2/z Capture/Publisher and the CDCzLog Publisher (used by IMS, VSAM, and Keyed file Compare captures) only. Warning: There is a potential for very high volumes of output.
[--enable-throttle \|--disable-throttle]	Turn on/off zlog write throttling in the IMS Log Capture and IMS Unload Utilities only.
[--enable-uow-tracker \| --disable-uow-tracker]	Turn on/off UOW tracking in the Db2/z Capture only. Warning: There is a potential for very high volumes of output.
[--uow-tracker-threshold=<uow_operations>]	Limits trace output to unit-of-work (UOW)'s with greater than or equal to the specified number of operations (inserts, updates, deletes) in the Db2/z Capture only. If not specified, the default is to trace all UOW's.

Note:

--enable-ack-trace generates one message in the log for every UOW published. If there is a high volume of "transactions", there will be a corresponding high number of messages that may result in S772 Abends.
When CF Structures are used for the z/OS System Logstreams, the IMS Log Capture and IMS Unload Utility components use a throttling technique to avoid offloads and keep data in the CF structure until it is Published and consumed by the downstream Engine(s). This provides better performance and more efficient use of CPU vs having the publisher retrieve data from offloaded datasets. Throttling is controlled by the specification of High and Low Offload percentages for structure utilization. It is important to size CF structures to avoid throttling if possible while at the same time to avoid offloads.

Throttling is turned on by default but can be turned off using either the sqdconf tune --disable-throttle or the runtime SQDPARMS option --ptk=14. Throttling slows down the LogStream (zlog) put process used by the Capture and IMS Unload utility to give publishers time to catch up and hopefully avoid offload. Its a crude control, and sometimes not very effective because It can cause capture to slow down. The Capture and Publisher do not communicate with each other to refine it. Some customers do however choose to disable throttling because they would rather have offloads occur than slow down change data capture or the unload utility.
--enable-uow-tracker can produce large volumes of output to SQDLOG that depend on transaction volume, number of tables per transaction, and the tracker threshold. Special planning and preparation may be required to avoid S722 ABEND.

Example 1

Display the latency for every Db2 UOW published.

sqdconf tune --enable-ack-trace /home/sqdata/db2cdc1/DB2CDC1.cab

00001523 92.06 [CDCSTORE] :ack:dcb060d805e6d13a commit:dcb060d546581402 latency:2881 ms
(cdc:////engine1)
00001524 92.06 [CDCSTORE] :ack:dcb060d805e70a38 commit:dcb060d546a9f402 latency:2880 ms
(cdc:////engine1)
00001525 92.06 [CDCSTORE] :ack:dcb060d805e74456 commit:dcb060d546f84402 latency:2879 ms
(cdc:////engine1)

Example 2

Display the latency for every IMS or VSAM or Keyed File Compare UOW published.

sqdconf tune --enable-ack-trace /home/sqdata/vsampub1/IMSPUB1.cab


00001523 92.06 [ZLOGC] :ack:dcb060d805e6d13a commit:dcb060d546581402 latency:2881 ms
(cdc:////engine1)
00001524 92.06 [ZLOGC] :ack:dcb060d805e70a38 commit:dcb060d546a9f402 latency:2880 ms
(cdc:////engine1)
00001525 92.06 [ZLOGC] :ack:dcb060d805e74456 commit:dcb060d546f84402 latency:2879 ms
(cdc:////engine1)

Example 3

Enable zlog write throttling in the IMS Log Capture.

sqdconf tune --enable-throttle /home/sqdata/imscdc1/IMSCDC1.cab

The UOW tracker is dynamically enabled and disabled with the SQDCONF tune command. If not disabled the trace will persists until the Db2/z Capture is unmounted. Setting the threshold is optional and can be done independently or in conjunction with enabling or disabling the trace. The threshold limits trace output to units of work with greater than or equal to the specified number of operations (inserts, updates, deletes). If not specified, the default is to trace all units of work. Output is written to SQDLOG and consists of two lines plus one additional line per table in the Unit of Work.

Note: This trace can produce large volumes of output to SQDLOG that depend on transaction volume, number of tables per transaction, and the tracker threshold. Special planning and preparation may be required to avoid S722 ABEND.

Example 4

Enable UOW Tracker and set the operation threshold to 200:

sqdconf tune --enable-uow-tracker --uow-tracker-threshold=200 /home/sqdata/db2cdc1/DB2CDC1.cab

//TUNEE EXEC PGM=SQDCONF,REGION=32M
//STEPLIB DD DISP=SHR,DSN=SQDATA.LOAD
//SYSPRINT DD SYSOUT=*
//SYSOUT DD SYSOUT=*
//SQDLOG DD SYSOUT=*
//SQDPARMS DD *
tune --enable-uow-tracker
--uow-tracker-threshold=200
/home/<%PREFIX_LLC%>/db2cdc1/DB2CDC1.cab
/*

Sample output for a small unit of work with operations to four tables (SQDATA.EMP1, .EMP2, .EMP3, .EMP4, three of which were activated for capture, one was not.

00012050 9e.00 [ DB2C] :uow:0000000000450E93B591 t:27 i:0 u:27 d:0 obj:4 commit
                       :bgn:DDB731D1773F434E end:DDB731D19C627B04 (152 ms) cid:SQDUSER1
                       :d:016d o:0003 p:0002 t:11 u:11 (SQDATA.EMP1)
                       :d:0150 o:0003 p:0002 t:11 u:11 (SQDATA.EMP2)
                       :d:017d o:0003 p:0002 t:5 (not source)
                       :d:0175 o:0003 p:0002 t:5 u:5 (SQDATA.EMP4)

Example 5

Disable UOW Tracker

sqdconf tune --disable-uow-tracker /home/sqdata/db2cdc1/DB2CDC1.cab


//TUNED EXEC PGM=SQDCONF,REGION=32M
//STEPLIB DD DISP=SHR,DSN=SQDATA.LOAD
//SYSPRINT DD SYSOUT=*
//SYSOUT DD SYSOUT=*
//SQDLOG DD SYSOUT=*
//SQDPARMS DD *
//SQDPARMS DD *
tune --disable-uow-tracker
/home/<%PREFIX_LLC%>/db2cdc1/DB2CDC1.cab
/*

tune - connect_cdc_sqdata - Latest

Connect CDC (SQData) Utilities