WADS fallback considerations

When you fall back from IMS 15.5 to a previous version of IMS, ensure that the WADS is allocated consistently with the prior version.

You must use a non-VSAM WADS data set in an IMS system of previous version.

If you defined WADS data set names for IMS 15.5 during migration that were different from the names used by the previous IMS version, use the previous names for fallback. The fallback process replaces the reference to the WADS data sets systematically. Otherwise, the WADS must be deleted and redefined after the IMS 15.5 system is shut down, and before the system is started at the previous IMS version.

At the end of fallback, cold start IMS with the FORMAT ALL or FORMAT WA keyword.