Code optimisation for siis instruction on a Z14 computer

Products

• Disk Backup and Restore - MVS
• DISK BACKUP AND RESTORE- ADD-ON OPTIO
• DISK BACKUP AND RESTORE

Issue/Introduction

During a study for program who doesn't conform on good practice guide, IBM said that some programs doesn't execute instructions on the good sequence, 

IBM doesn't give us the name of the program, but at this time frame there is only archiving CA-DISK jobs. 

To investigate,do a Strobe analysis on Ca Disk archiving/backup jobs.

It seems that ADSDB001 ( at offset 2c0 length 64) , KWIKSHR4 ( at offset 100 length 64),  ADSMI0002 (at offset 80 length 64), ADSUT042 ( at offset 280 length 64) and GSMFSCRN  ( at offset 500 length 64)  are programs who have the more CPU impact.

Here is the link to IBM site to understand the problem and have examples: http://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/WP102806

For IBM study there is more than 5% overhead. How to get it fixed?

Environment

Release : 12.5

Component : CA Disk Backup and Restore

Cause

The EDF data with the new version of the CP3EXTR utility produces report that does have the SIIS violations in ADSMI002. In the doc we've seen so far (Strobe reports and HIS data), the other top CPU consumers were just heavy-hitter modules and didn't have any SIIS problems in the sections of code that the tools were reporting on.

 

  The SIISP vector that's now in the report is extremely helpful. It does show that the SIIS percentage is showing up when the job starts. The vector that is in the EDF output shows a SIIS % of 4.2% as the highest SIIS percentage from any of the reporting intervals, and this interval was when the job started. For the 5-minute interval, the job started 3 minutes into that interval. 

 

   There is a doc from IBM (the first one listed at http://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/WP102806) that mentions the following about SIIS percentages and when they should be addressed:

 

Resolution

Apply the Apar ST15101.