Migration control data set

The migration control data set (MCDS) provides information about migrated data sets and the volumes they migrate to and from. Additionally, internal processing statistics and processing-unit-environment data reside in the MCDS. DFSMShsm needs this information to manage its data sets and volumes. With this information you can verify, monitor, and tune your storage environment.

Migration Control Data Set (MCDS)

Required:

Yes.

Allocated by starter set:

Yes, see Starter set example.

Maximum record size:

2040 bytes.

Data set type:

VSAM key-sequenced data set (KSDS).

Storage guidance:

See Considerations for DFSMShsm control data sets and the journal.

An MCDS residing on a DASD device that is shared by two or more processors defines a multiple DFSMShsm-host environment to DFSMShsm. DFSMShsm assumes that there is more than one host sharing the MCDS, BCDS (optional), and OCDS (optional), if the MCDS is on shared DASD or the user specifies CDSSHR=RLS or CDSSHR=YES.

The control data sets are backed up at the beginning of automatic backup and are backed up differently from user data sets. The way control data sets are backed up depends on how you specify the SETSYS CDSVERSIONBACKUP command. For more information about specifying the CDS backup environment, see Defining the backup environment for control data sets.

For information about control data sets in a multiple DFSMShsm-host environment, see CDS considerations in a multiple DFSMShsm host environment.

DFSMShsm also writes two kinds of statistics records in the MCDS: daily statistics records and volume statistics records. DFSMShsm updates these records every hour if any data sets have changed. DFSMShsm writes the two statistics records to the system management facilities (SMF) data sets if you specify the SETSYS SMF command.