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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 are "applied" immediately unlike most SQDCONF parameters that require the Stop/Apply/Start sequence.

Syntax

sqdconf tune <cab_file_name>

[--enable-ack-trace |--disable-ack-trace]

[--enable-throttle |--disable-throttle]

 

Keyword and Parameter Descriptions

[--enable-ack-trace |--disable-ack-trace] - Turn on/off diagnostic ACK (Acknowledgment) 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). WARNING: Potentially Very High volume of output.

[--enable-throttle |--disable-throttle] - Turn on/off zlog write throttling in the IMS Log Capture and IMS Unload Utilities ONLY.

Notes:

1.--enable-ack-trace generates one message in the log for every unit-of-work (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.

2.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. It's a crude control, and sometimes not very effective because It can cause capture to slow down. The Capture and Publisher don't 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.

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