IBM SC34-7012-01 manual VSAM access method services, Invalid state changes for BWO attributes

When you use DFSMShsm, you still use DFSMSdss as the data mover. You can specify this using the DFSMShsm SETSYS command:

SETSYS DATAMOVER(DSS)

The DFSMS processing at the start of backup is dependent on the DFSMS release level. For releases before DFSMS 1.2, DFSMSdss first checks the BWO attributes in the ICF catalog to see if the data set is eligible for BWO. If it is, the backup is made without attempting to obtain exclusive control and serialize updates to this data set.

For DFSMS 1.2 onward, DFSMSdss first tries to obtain exclusive control of the data set. If DFSMSdss succeeds, an enqueued form of backup takes place. If this serialization fails, DFSMSdss checks the BWO attributes in the ICF catalog to see if the data set is eligible for BWO. If it is, a BWO backup is attempted. If it is not eligible, the backup attempt fails.

This change will prevent DFSMS starting a BWO backup after CICS has abnormally terminated.

At the end of the BWO backup, DFDSS again checks the BWO attributes. If the data set is no longer eligible for BWO, the backup is discarded. Events that cause this situation are:

vFile closing during BWO, which sets the ‘BWO disabled’ state

vStart of VSAM split, which sets the ‘BWO enabled and VSAM split in progress’ state

vEnd of VSAM split, which sets the ‘BWO enabled/disabled and VSAM split occurred’ state.

At the start of a backup, if the state is ‘BWO enabled and VSAM split occurred’, DFSMSdss resets the state to ‘BWO enabled’. Then, if another VSAM split occurs, the backup will be discarded at the end of the backup operation.

VSAM access method services

DFSMS access method services import and export operations do not support BWO in releases earlier than DFSMS 1.2. Access method services always serializes the data set before exporting it; and when the IMPORT function is used, the BWO attributes in the ICF catalog are not updated.

For DFSMS 1.2 onward, access method services supports the import and export of BWO attributes.

Invalid state changes for BWO attributes

CICS, DFSMSdfp, DFSMSdss, and an SMSVSAM server can all update the BWO attributes in the ICF catalog.

To prevent errors, DFSMSdss fails a BWO backup if one of the following state changes is attempted during the backup:

vFrom ‘BWO enabled and VSAM split in progress’ to ‘BWO enabled’. This state change could be attempted if:

1.At the start of data set backup processing, a request is issued to change the ‘BWO enabled and VSAM split occurred’ state to the ‘BWO enabled’ state.

2.But then, before the ‘BWO enabled’ state is set, a VSAM split occurs and sets the ‘BWO enabled and VSAM split in progress’ state.

214CICS TS for z/OS 4.1: Recovery and Restart Guide