IBM SC34-7012-01 manual BWO processing

After an uncontrolled or immediate shutdown, further BWO backups might be taken by DFSMShsm, because the BWO status in the ICF catalog is not reset. These backups should be discarded; only the non-BWO backups taken at the end of the batch window should be used during forward recovery, together with the CICS forward recovery logs.

Data set security: CICS must have RACF ALTER authority for all data sets that are defined as BACKUPTYPE(DYNAMIC), because CICS needs to update the BWO attributes in the ICF catalog. The authority must apply either to the data set or to the ICF catalog in which the data set is cataloged. For information on defining RACF ALTER authority, see the CICS RACF Security Guide.

BWO processing

The information in the remainder of this section might be required by the system administrator to recover from error situations due to incorrect operating procedures or hardware failures.

The main data fields used by the BWO facility are:

vAttribute flags in the ICF catalog, to control BWO activity. The DFSMSdfp field dictionary name is VVRSMFLG. For more information about the attribute flags used in connection with BWO, see DFSMS/MVS Managing Catalogs.

vRecovery point in the ICF catalog. This point is the time from which the forward recovery utility must start applying log records. It is always before the time that the last backup was taken. It is recorded in local time format (0CYYDDDF HHMMSSTF) where:

C= century (0=1900, 1=2000, etc.) YY = year

DDD = day HH = hours MM = minutes SS = seconds

T = tenths of a second F = + sign

The DFSMSdfp field dictionary name is VVRRDATA.

vThe BACKUPTYPE attribute in the CICS file resource definition (for DFSMS 1.2), or the BWO option in the ICF catalog (for DFSMS 1.3). When CICS has determined the BWO option from one of these sources, it stores the value into the data set name block (DSNB) for the base cluster at the time the first file referencing the data set is opened.

The attribute flags and recovery point are managed by VSAM in the primary data VSAM volume record (VVR) of the base cluster, which is in the VSAM volume data set (VVDS). There is only one primary base cluster VVR for each VSAM sphere, which is why BWO eligibility is defined at the sphere level. For more information, see DFSMS/MVS Managing Catalogs.

BWO processing affects the following operations in a CICS system:

vFile opening

vFile closing

vShutdown and restart

vData set backup and restore

vJournaling and forward recovery logging

vForward recovery

Chapter 18. Backup-while-open (BWO) 209