In specific scenarios it makes sense to change the access method for the IMS primary database
from VSAM/ESDS to OSAM (e.g. if the dataset is going to reach the 4GB limit for VSAM datasets).
This document lists the steps being necessary to convert from VSAM/ESDS to OSAM.
These are the steps being necessary to change the IMS database dataset access method from VSAM/ESDS to OSAM :
Because the old Recon entries (belonging to the VSAM database) are still present in DBRC, database recoveries to a
timestamp BEFORE changing the database to OSAM are still possible (but of course the OLD VSAM-DBD must be used
for this recovery run, a different database dataset should be used (to keep the current OSAM database), and the recovery
run entry should NOT be registered to DBRC).
If recoveries to the old VSAM database are not wanted anymore, the old Recon entries could be deleted by deleting/
redefining this database to DBRC after re-genning the new DBD (step 6.).