Volume serialization

For volume serialization, DFSMSdss issues the RESERVE macro against the volume to prevent direct access device storage management (DADSM) functions (such as addition, deletion, extension, or renaming of data sets) from changing the VTOC entries during DFSMSdss processing. The RESERVE is issued before processing is begun on a particular volume, and released when processing is completed, during the following operations:

DUMP (except logical)
CONSOLIDATE
COPY (except logical)
RESTORE (except logical and physical data set)
PRINT (except data set)
DEFRAG

Note: Be aware that volume serialization (RESERVE performed against the volume) does not ensure integrity at the data set level. For example, in the case of a physical full volume dump, data sets are not serialized and the data sets could change while the DUMP is being taken.

Note that you can use the DFSMSdss enqueue installation exit to request that DFSMSdss only reserve the VTOC for the duration of VTOC access during the following operations:

Full, tracks, and physical data set DUMP
Full and tracks COPY
Tracks PRINT

In addition, DFSMSdss issues the RESERVE macro against a volume while updating information in the VTOC, such as the RACF-defined flag and the data-set-changed flag. DFSMSdss also issues the RESERVE macro against a volume while accessing the information in the VTOC to perform data set selection during the following operations:

Logical DUMP with input volumes specified
Logical COPY with input volumes specified
CONVERTV
COMPRESS
RELEASE

Related reading: For more information about the enqueue installation exit routine, see z/OS DFSMS Installation Exits.