Hardware performance options

Use CACHE and DASD-FAST-WRITE if you can for the files recommended below. While these facilities do not reduce the number of EXCPs, they can sharply reduce the time it takes to complete them. CACHE and DASD-FAST-WRITE can be important ways to reduce enqueue contention for two reasons. First, DASD-FAST-WRITE can reduce the write times. VSAM buffering, of course, only reduces the read times, and that can make write-time reductions even more important. Second, both CACHE and DASD-FAST-WRITE are effective on spanned records.

CACHE

Appropriate for all files except the job-tracking logs. The best candidates are:

• The long-term plan (EQQLTDS)
• Operator instructions (EQQOIDS)
• Application descriptions and JCL variable tables (EQQADDS)
• The JCL libraries (EQQJBLIB)
• Event data sets (EQQEVDS), but only when an event reader task has been started using the ERDRTASK keyword on the OPCOPTS initialization statement.

DASD-FAST-WRITE

Suitable for all files. The best candidates are:

• The job-tracking logs (EQQJTnn)
• Submit/release data sets (EQQSUDS)
• The JCL repository (EQQJS1DS and EQQJS2DS)
• Event data sets (EQQEVDS)
• Current® plan data sets (EQQCP1DS and EQQCP2DS).