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:
  • Attribute 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 z/OS® DFSMS Managing Catalogs.
  • Recovery 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.
  • The 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 z/OS DFSMS Managing Catalogs.

BWO processing affects the following operations in a CICS system:
  • File opening
  • File closing
  • Shutdown and restart
  • Data set backup and restore
  • Journaling and forward recovery logging
  • Forward recovery
Each of these operations is discussed in the following sections.