Deciding which VSAM spheres to protect

You want to be able to forward recover all VSAM spheres that are defined as CICS® files. Data sets that are read-only or browse-only do not need forward recovery or backout, however, back them up regularly in case they become unusable.

Ensure that you define your VSAM base clusters and alternate index (AIX®) data sets with SHAREOPTION 1 or SHAREOPTION 2. You can do this by using the SHAREOPTION parameter of the appropriate access method services (AMS) command, such as the DEFINE CLUSTER command or the ALTER command. SHAREOPTION 3 and SHAREOPTION 4 are not suitable for CICS, because CICS cannot prevent concurrent write access to the data sets by other CICS regions or by batch jobs.

If you must use SHAREOPTION 3 or SHAREOPTION 4 with multiple CICS regions sharing the same VSAM sphere, you must use unique ddnames across different systems. Unique ddnames ensures the correct sequencing and enables CICS VR to correctly process the log records for forward recovery. See the SHAREOPTION description in z/OS® DFSMS Access Method Services for more information about the risks involved with SHAREOPTION 3.