Performance with IDMS batch job doing area sweep

Products

• IDMS
• IDMS - Database

Issue/Introduction

An IDMS batch job reads an entire IDMS area doing an area sweep. Over time, the job execution time is increasing.

Is an unload and reload of the area required?

Environment

Release: 19.0

Resolution

For area sweep processing an unload/reload will not help.
Since the program only reads the database try running the job in local mode which will increase performance.
Then there are 2 other options that can be used for local mode jobs:

• Use PREFETCH processing by specifying PREFETCH=ON in SYSIDMS. Note PREFETCH is automatically turned on if the buffer for the area has more than 255 pages.
  
  
• Use QSAM processing by specifying IDMSQSAM=ON and QSAMAREA=qsam-area-name in SYSIDMS

Use the SYSIDMS BUFFERSTAT parameter to obtain statistics before and after the change.

Additional Information

See documentation section SYSIDMS Parameter Descriptions and Using Chained Reads.

Also see article PREFETCH: how it is enabled/disabled and when to use it