How you request BWO

There are two ways in which files can be defined as eligible for BWO:

  1. By specifying the BWO option for the data set in the ICF catalog
  2. By specifying the BWO option on the CICS® file resource definition in the CSD

Defining BWO in the ICF catalog requires DFSMS 1.3. For data sets that are accessed in RLS mode, the BWO option must be defined in the ICF catalog. Data sets that are accessed only in non-RLS mode can be defined either in the ICF catalog or in the CICS file definition. If BWO is defined in the ICF catalog definition, it overrides any BWO option defined in a CICS file definition.

Note:
Requesting BWO for the CICSPlex® SM data repository via the IDCAMS DEFINE CLUSTER definition within the ICF catalog is not recommended, performance is degraded. . See the CICS Transaction Server for z/OS Installation Guide for information on taking backups of the CICSPlex SM data repository.

Specifying BWO using access method services

There is a BWO parameter on the access method services DEFINE CLUSTER statement. You can specify the BWO parameter as follows:

TYPECICS
The data set is eligible for BWO in CICS.
NO
The data set is not eligible for BWO.
TYPEIMS
The data set is eligible for BWO in IMS™, but CICS treats this as NO.
TYPEOTHER
The data set is eligible for BWO, but CICS treats this as NO.

Start of changeIf you specify BWO(TYPECICS), you might need to know whether the PTF associated with APAR OA04220 has been applied to your z/OS® system. That APAR extended the capabilities of VSAM so that BWO processing for RLS is no longer disabled for non-recoverable files.

End of change

If you omit the BWO parameter from the DEFINE statement, by default it is UNDEFINED in the ICF catalog, and the BWO attribute from the CICS file resource definition is used.

BWO(TYPECICS) is the equivalent of BACKUPTYPE(DYNAMIC) in a CICS file resource definition. All other values, including UNDEFINED, are treated by CICS as the equivalent of BACKUPTYPE(STATIC) in a CICS file resource definition. For simplicity, the CICS terms BACKUPTYPE(DYNAMIC) and BACKUPTYPE(STATIC) are used unless it is necessary to specifically mention the access method services BWO parameters.

Specifying BWO for the CSD

The BWO options for the CSD are taken from the ICF catalog if they are defined there, and the system initialization parameters (CSDBKUP, CSDRECOV, and CSDFRLOG) are ignored.

Specifying BWO on CICS file resource definitions

You define a file as eligible for BWO with the BACKUPTYPE attribute on a CICS FILE resource definition in the CSD.

If you specify BACKUPTYPE(DYNAMIC), the file is defined as eligible for BWO when the data set is opened. You must also specify RECOVERY(ALL) and FWDRECOVLOG(nn) to request forward recovery support.

BACKUPTYPE(STATIC), the default, defines a file as not eligible for BWO. In this case, if DFSMShsm is to back up a data set, all CICS files currently open for update against that data set must be closed before the backup can start.

All files opened against the same VSAM base cluster must have the same BACKUPTYPE value. That value is established by the first file opened against the cluster; it is stored in the CICS data set name block (DSNB) for the cluster. If the value for a subsequent file does not match, the file-open operation fails.

The BACKUPTYPE value in the DSNB persists across warm and emergency restarts. It is removed by a CICS cold start (unless a backout failure occurs) or by issuing EXEC CICS SET DSNAME ACTION(REMOVE) (or the CEMT equivalent) for the base cluster data set. To do this, all files that are open against the base cluster and via path definition must be closed, and the DSNB must have FILECOUNT of zero and NORMALBKOUT state.

The BACKUPTYPE attribute is ignored for user-maintained data table base clusters, because no forward recovery support is provided.

BWO for CSD

To use BWO for the CSD file, specify the CSDBKUP=DYNAMIC system initialization parameter. Also specify CSDRECOV=ALL and CSDFRLOG=nn to request forward recovery support.

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