Multi-file tapes where all files have been uncataloged are not always being scratched. Causing our DLM to fill will unneeded data. In our options I see the following set:
These tapes are mainly GDGs.
Found that he had a lot of tapes with the OSC bit turned on but the tape DSN was not cataloged. Most of these were very old and may have been rolled off in an earlier release, and MIXGDG in the earlier release was set to NO. Had him run TMSOSCAT RESYNC,DETAIL and that corrected the OSC bits and he was able to scratch a large number of tape and freed up about 30% of the DLM storage.
You need to be careful with TMSOSCAT if all of your catalogs are not connected to one system.
If the catalogs are not all connected you would need to run on the largest system (most catalogs), TMSOSCAT PARM=(RESYNC,DETAIL). Then when it is done on all other systems you would run TMSOSCAT,PARM=(SYNC,DETAIL). The first run of TMSOSCAT will set the OSC bits coorrectly according the catalogs it has access too. The other runs will then only update those records where the OCS bit is off but we find a catalog entry in a catalog that was not connected to the system where the RESYNC was done. This must complete before the next run of TMSCLEAN.