Operation of the BWO facility

To use the backup-while-open facility with CICS® VR, define DFSMSdss™ as the method DFSMShsm™ uses to move data.

You can specify this using the DFSMShsm™ SETSYS command: 
SETSYS DATAMOVER(DSS)

When DFSMSdss™ performs a logical dump, it examines the backup-while-open flags in the integrated catalog facility (ICF) catalog and reports on the success or failure of the backup. For example, if a VSAM control interval (CI) or control area (CA) split is in progress at the start of a backup, the backup is not made. Also, if a split occurs during a backup-while-open backup, or a split is still in progress after a backup, the backup is logically discarded by DFSMShsm™. If you are using DFSMSdss™ without DFSMShsm™, examine the reports that DFSMSdss™ produces to find out if the logical dump has been successful. But, if you use the concurrent copy function with BWO, CI or CA splits do not affect the contents of the copy that is being made. See Using the concurrent copy function with CICS VR for more information.

Because the process of making backups can lead to increased I/O activity, consider making backups during periods of low activity. This would avoid an effect on the response time of the online application and reduce the probability of CI or CA splits.

For more information about DFSMSdss™ see z/OS® DFSMSdss™ Storage Administration Guide. For more information about DFSMShsm™, see z/OS® DFSMShsm™ Storage Administration Reference.

The master terminal operator (MTO) must be aware of any new environment. Before the availability of the backup-while-open facility, to backup a VSAM sphere, the MTO would quiesce all transactions that would update the data set, notify the users, and close and deallocate the necessary files. These procedures are not needed with the backup-while-open facility.

With the backup-while-open facility, the MTO receives a message if an application attempts to open a file that is flagged as back level. This check occurs regardless of whether you specify the BACKUPTYPE option DYNAMIC or STATIC for the file. A back-level data set is one that has been:
  • Identified by the ICF catalog as corrupt.

    If this situation occurs, the following messages are issued, and the MTO must restore and recover the VSAM sphere to ensure data integrity:

    DFHFC5801A
    applid File OPEN has failed for VSAM data set. The BWO values in the ICF catalog indicate that the data set needs to be restored and forward recovered. Data set 'dsname'.
    DFHFC5806
    applid File OPEN failed. DFHFCAT returned an error response from a BWO action on a VSAM data set. File 'filename' data set 'dsname'.
  • Restored from a backup copy but not recovered.
  • Forward recovered, but the forward-recovery operation has not completed successfully.
    In either of these cases, the following messages are issued, and the MTO must decide if the backup copy had been restored but not recovered, or if recovery has failed:
    DFHFC5802A
    applid File OPEN has failed for VSAM data set. The BWO values in the ICF catalog indicate that data set needs to be restored and forward recovered. Data set 'dsname'.
    DFHFC5806
    applid File OPEN failed. DFHFCAT returned an error response from a BWO action on a VSAM data set. File 'filename' data set 'dsname'.

If recovery was not run, you can run CICS® VR to recover the VSAM data set. If the messages are issued because of the failure of CICS® VR recovery, the MTO must restore and recover the associated VSAM sphere to ensure data integrity.

If an application attempts to open a file that is eligible for backup-while-open processing in the ICF catalog, but is not defined as such in the CICS® file definition, the following actions occur:
  • The ICF catalog is set to show that the data set is not eligible for backup-while-open processing.
  • The recovery point is updated to the time held in the MVS™ system clock , see BWO and the recovery point time.
  • This warning message is issued at the MTO console:
    DFHFC5809
    applid File OPEN warning. BACKUPTYPE attributes conflict with BWO values defined in ICF catalog. BWO values have been updated. File 'filename' data set 'dsname'.
  • The MTO can use this command to ask whether the first file to be opened against a data set name was indicated as eligible for backup-while-open processing: 
    CEMT INQUIRE DSNAME

    For more information, see CICS® Supplied Transactions.

    Note:
    When you are recovering a restored data set that was backed up using the backup-while-open facility, record not found and duplicate record messages are not reported, but statistics indicating these conditions are in the report. You can analyze and act on these messages if you have provided an error exit for this purpose. The CICS® VR error exit is called for all types of VSAM errors.