Increased dirty read errors after enabling MEMORY CACHE

Products

• IDMS

Issue/Introduction

After enabling MEMORY CACHE for some database files, it is possible to encounter a much increased incidence of dirty read errors.

Environment

Release : All supported releases.

Cause

MEMORY CACHE is enabled in the INCLUDE FILE section of the DMCL definition, and there is no differentiating between CV mode and local mode as there is with BUFFER definitions. Therefore, by default, enabling MEMORY CACHE turns it on for both CV mode and local mode processing.

This has the effect of implementing a large buffer for local mode jobs and so increases the likelihood of encountering invalid abends due to dirty reads. Furthermore most local mode processing is typically area sweep based which means they probably don't benefit much from MEMORY CACHE anyway.

Resolution

Currently there is no easy way to enable MEMORY CACHE in CV only.

Suggestions:

1. Disable it in the DMCL and use DCMT commands to dynamically enable it in the CV at startup.
2. Use different DMCLs for CV and local mode processing.

Additional Information

Does the MEMORY CACHE option work in local mode?
Data Space and Memory Caching in IDMS
COMMIT of updates when using MEMORY CACHE