Using the VSAM-Statistics report

From a VSAM-Statistics report, you can determine which calls in an application program require a great many I/O operations. After you know this, you can improve performance by tuning either the database or the application program to reduce I/O operations.

The following fields in the report tell actual I/O activity and are therefore the most important ones to monitor:

• READS
• USR WTS
• NUR WTS

If you can reduce the averages in these fields, performance can be improved.

In tuning to reduce I/O operations, pay most attention to calls issued a large number of times. It is more profitable to save 1 second on a call executed 2000 times than to save 5 seconds on a call executed ten times (2000 versus 50 seconds). The DL/I-Call-Summary report (discussed under DL/I-Call-Summary report) describes how many times each DL/I application program call is issued.