When you recover a volume, vary the volume offline to sharing systems. This is done with the VARY command. However, VARY might not work because a VVDS or BCS on the volume is allocated to the catalog address space. Use MODIFY CATALOG,ALLOCATED to determine if there are any open BCSs on the volume.

You can unallocate a BCS from CAS with the MODIFY CATALOG,UNALLOCATE command. The VVDS can be unallocated with the MODIFY CATALOG,VUNALLOCATE command. Neither of these MODIFY CATALOG commands locks the BCS or VVDS, so issue the VARY command before unallocating them. The DISPLAY command can be used to help determine if the VVDS or BCS on the volume is allocated.

When you recover a volume, the physical location of the volume's VVDS might change. Because the catalog address space maintains control blocks for each VVDS, this change of location might make VSAM and SMS-managed data sets on the volume inaccessible.

If you unallocate the VVDS, the control blocks are rebuilt after a request for the volume is processed by catalog management. If data sets remain inaccessible after the recovery, close the VVDS with MODIFY CATALOG,VCLOSE. If data sets remain inaccessible, the problem is not with the control blocks for the VVDS.

The same considerations hold true if there is a BCS on the volume: the control blocks for the BCS are rebuilt by the first request that uses the catalog. If you have problems accessing the catalog, unallocate it or close it. Doing either solves problems of inaccurate control blocks.

Do not use MODIFY CATALOG in place of varying a volume offline. Closing or unallocating a VVDS or a BCS does not prevent users from accessing a volume. MODIFY CATALOG is best used to unallocate a BCS or VVDS from the catalog address space, so that the VARY command can be performed.