When creating a backup copy of the DFSMSrmm control data set, care must be taken to avoid creating a fuzzy backup. A fuzzy backup means that the control data set was in one state when the backup started, but in another state by the time the backup finished. As a result, the backup copy could represent an inconsistent state for the control data set and could be useless, because a restore would yield inconsistent CDS records.

You can create a consistent copy of the DFSMSrmm control data set using any of the following methods:

1. EDGHSKP/EDGBKUP BACKUP

   The target of the BACKUP request is a VSAM KSDS (AMS REPRO is used). You can optionally use forward recovery to a more recent level of the CDS by means of journal or DFSMSrmm SMF records. If BACKUP(AMS), or BACKUP(DSS) without concurrent copy, is used, the backup processing prevents updates to the DFSMSrmm control data set until the backup completes.

2. EDGHSKP/EDGBKUP followed by RESTORE (AMS or BACKUP(DSS) backup can be used)

   BACKUP(DSS) creates a portable data set by means of the DFSMSdss DUMP command. You can optionally use forward recovery to a more recent level of the CDS by means of journal or DFSMSrmm SMF records. If BACKUP(AMS), or BACKUP(DSS) without concurrent copy, is used, the backup processing prevents updates to the DFSMSrmm control data set until the backup completes.

3. EDGHSKP/EDGBKUP with the BACKUP(COPY) parameter This ensures that a consistent, non-fuzzy, copy is created under DFSMSrmm control. No forward recovery is needed unless a more recent point in time of the CDS is required.
4. XRC, PPRC, Metro Mirror, Global Mirror

   These options use DASD mirroring technologies to create a copy of the CDS. Forward recovery from journal records is required to ensure the copy is not fuzzy. Although the mirroring technologies create copies that are consistent with the source data, because of the way DFSMSrmm updates its CDS, the CDS records themselves might not be consistent. The journal records are written before the CDS is updated, so the most recent complete set of journal records can be used to de-fuzz the CDS.

5. FlashCopy

   RMM must be quiesced or stopped to ensure that a CDS copy is not “fuzzy”. For Volume or Data Set Level (FlashCopy V2), the DASD subsystem must be a FlashCopy capable disk subsystem Forward recovery from journal records is required to ensure the copy is not fuzzy.