After upgrading an IDMS CV to a new release, it may prove necessary to fallback to a prior release.
If I need to fallback or downgrade my IDMS CV to an earlier release, what ar the recommended steps to do that?
This situation can arise in any environment running an IDMS CV.
To fallback to an earlier release, several steps are necessary:
1- Shutdown CV.
2- Change all JCL to point to the IDMS load libraries used in the previous release.
3- Initialize the journal files with the FORMAT utility using the previous release IDMS load libraries.
4- Offload or initialize the log file using the previous release IDMS load libraries.
5- If any dialogs or application programs have been recompiled under the new release, as long as they do not make use of new features introduced on that release, then they should run fine after the CV is restored to an earlier release.
6- Any application dialog or program code that takes advantage of a new feature on the upgraded release level, will not function properly when the CV is restored to an earlier release. The code must either be converted back to its former state, or the references to the new features must be removed.
7- Bring up CV.
1- Usually, the SVC of newer releases is downward compatible and can be used with prior releases.
2- After running the CONVERT CATALOG utility, the resulting catalog is usually compatible with all previous releases. There is no need to roll this back. The caveat to this is when there are views defined on tables in the SYSTEM schema. After the upgrade you will need to re-create any views that are defined on the SYSTEM tables. If you then rollback to a prior release, you will need to keep the new view definitions that are based on the changes that happened when you ran the CONVERT CATALOG step as part of the install.
3- User database files are compatible across all releases.
To check for any specific considerations involved when there is a need to fallback to a previous release, check the Release Notes for the genlevel to which you upgraded. If there are any release-specific considerations involved in doing a fallback, they will be recorded in that guide.