Once the Log Reader configuration (.cab) file has been created, JCL similar to sample member SQDIMSC included in the distribution is used to start the Log Reader Capture Agent process.
While the SQDCONF utility is used to create the Capture Agent configuration and perform most of the other management and control tasks associated with the capture agent, on z/OS it cannot perform the function of the MOUNT command, used on other platforms to bring the agent on-line. On z/OS that function is performed by a Capture Agent specific JOB. Once the Capture Agent JOB has been Started on z/OS, the sqdconf utility can be used to Stop and Pause the Capture. While the SQDCONF utility is used to make changes to the the Log Reader Capture CAB file that can only be done when the capture is not running.
When CF Structures are used for the z/OS System Logstreams , the IMS Log Capture and IMS Unload 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 --ptk=14. Throttling slows down the LogStream (zlog) put process used by the Capture 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 with the PTK because they would rather have offloads occur than slow down change data capture.
//SQDIMSC JOB 0,MSGLEVEL=(1,1),MSGCLASS=H,REGION=0M,NOTIFY=&SYSUID
//*
//*--------------------------------------------------------------------
//* Execute the IMS Log Capture Agent - SQDIMSC
//*--------------------------------------------------------------------
//* Required parameters (lower case):
//* config_file - Specifies the fully qualified name of the
//* predefined IMS capture agent configuration
//* file (see sample JCL SQDCONIC)
//*
//* Optional parameters (lower case):
//* --ziip - Instructs the capture to utilize zIIP engines for
//* Logstream processing
//* --ptk=14 - Disables throttling
//*
//* Notes:
//* 1) Parameter Keywords Must be Entered in lower case
//* 2) Parameters Values are Case Sensitive
//* 3) Change the SET parms below for:
//* HLQ - high level qualifier of the CDC PGMOBJ & LOADLIB
//* VER - the 2nd level qualifier of the CDC PGMOBJ & LOADLIB
//* PROCVER - the 2nd level qualifier of the CDC PROCLIB
//* IMSRESL - the name of the IMS RESLIB
//*--------------------------------------------------------------------
//*
// SET HLQ=SQDATA
// SET VER=V400
// SET PROCVER=V400
// SET IMSRESL=DFSE10.SDFSRESL
//*
//*--------------------------------------------------------------------
//CDCPROCS JCLLIB ORDER=&HLQ..&PROCVER..PROCLIB
//*
//JOBLIB DD DISP=SHR,DSN=&HLQ..&VER..LOADLIB
// DD DISP=SHR,DSN=&IMSRESL
//*
//*--------------------------------------------------------------------
//SQDIMSC EXEC PGM=SQDIMSC
//*SQDIMSC EXEC PGM=XQDIMSC
//SYSPRINT DD SYSOUT=*
//CEEDUMP DD SYSOUT=*
//SYSUDUMP DD SYSOUT=*
//*SQDLOG8 DD DUMMY
//SQDLOG DD SYSOUT=*
//*
//*SQDPARMS DD DISP=SHR,DSN=&HLQ..&PROCVER.PARMLIB(IMSCDC)
//SQDPARMS DD *
/home/sqdata/IMSCDC.cab
/*
--ziip /home/sqdata/IMSCDC.cab
--ziip --ptk=14 /home/sqdata/IMSCDC.cab