FILE_BUF SYSIDMS parameter in IDMS

Products

• IDMS - Database

Issue/Introduction

The SYSIDMS parameter FILE_BUF can be used to dynamically add pages to a local mode buffer over and above what is defined in the DMCL.

How is the parameter really used with respect to the DDNAME specified?

Environment

Release : All supported releases.
Component : IDMS/DB

Resolution

The FILE_BUF parameter is specified in the SYSIDMS file as follows:

FILE_BUF=EMPDEMO=100

What this statement does is it looks in the DMCL for the buffer that ddname EMPDEMO maps to and adds 100 pages to that buffer.
Any other files that also map to that buffer will therefore reap the benefit of that setting.

Furthermore, if there are multiple FILE_BUF settings for different ddnames that map to the same buffer, then all of the assigned buffer amounts will be added.
For example, consider this:

FILE_BUF=EMPDEMO=100
FILE_BUF=INSDEMO=100
FILE_BUF=ORGDEMO=100

If EMPDEMO, INSDEMO and ORGDEMO all map to the same buffer, then that buffer will have 300 pages added to it.

Also they are all added up and used when the buffer is first opened and so the number of the pages in the buffer does not "grow" as each individual file is accessed.