SYSVIEW usage of Exits and Cpu Usage
Article ID: 76608
Updated On:
Products
Issue/Introduction
We have got a question from a customer regarding Sysview and CPU usage. We have changed CICSOPTS parameters : All DATA COLLECTION for FC, TS and DB2 to NO and saved many MIPS. But unfortunately, we have some complaints:
Q1) CPU usage for DB2 DATA COLLECTION is decreased, but it does not disappear completely according to CGBLEXIT. Programs GSVCG072 and GSVCG073 are still in use for DB2. We estimate its cost to > 40 MIPS on a peak hour, this just to give us the number of DB2 CALLS we already have from our CICS accounting record!
Q2) User exits XFCFRIN and XFCFROUT are used i.e. with a READ FILE. A trace for AP domain at level 2 shows many trace points.
Q3) User exits XTSQRIN and XTSQROUT are used i.e. with a READQ-TS. A trace for AP domain at level 2 shows many trace points. We have not seen this problem in the two PROD AOR regions we have traced, but it appears in the here attached trace from a SYSTEMTEST AOR region. We don't know how much FC and TS exits cost, but this cannot be free of charge. Do we need to set further options? I will attach a Cics trace from SYSTEM TEST cics SYSTAORB and a print of CICSOPTS via Sysview print command PRINT of SYSTAORB and a production cics PRODAORH
Environment
Component:
Resolution
A1) The GSVCG072 and GSVCG073 are responsible for monitoring DB2 requests, yes, but they are responsible for monitoring MQ and a few other things that go through CICS's Resource Manager (RM) exit point. These exit points can be called many times per transaction and can cause additional overhead if you do not require the DB2/MQ timing in the CICS transaction record that SYSVIEW creates. To completely disable these exits, you will need to ensure all three of these CCONFIG options are set to no:
TRANSACTION-DATA-RSCEMGR
TRANSACTION-DATA-DB2
TRANSACTION-DATA-WEBMQ
It currently appears you have TRANSACTION-DATA-WEBMQ set to YES, thus this is why you set the RM exit point still active. If you do not require MQ timing data in the CICS transaction record, then you can safely set this option to NO.
Based on the CGBLEXIT capture you sent in, the RM exit point was over 1/2 of the total exit overhead. Shutting this off will by far have the most impact to the reduction of CPU.
A2) The File Control (FC) exit points typically do not cause the overhead that the RM exits do. You can turn this exit of by setting TRANSACTION-DATA-FILES to NO. It appears you have already done this. If you do not require file timing data in your CICS transaction record, then you can safely leave this option set to NO.
I will also note that at SYSVIEW 15.0 a new feature was added that allows SYSVIEW to collection File Control information without the use of the File Control exit point. It adds nearly no overhead to CICS as CICS is already tracking this information internally. This was added as a PTF in SYSVIEW 15.0: RO99412. If you are going to upgrade SYSVIEW soon, I would suggest looking into adding PTF RO99412, then set TRANSACTION-DATA-FILES to SUMMARY to enable this feature.
A3) The Temp Storage (TS) exit points are responsible for timing temp storage requests and again typically do not cause much over head compared to the RM exits. If you do not require temp storage request timing data in the CICS transaction record, then the TRANSACTION-DATA-TEMPSTG can be set to NO to disable these exits. It appears you have already done this.
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