Recoverable and nonrecoverable data sets

CICS® file control supports a recoverable/nonrecoverable data set concept. The data set definition includes a recoverability attribute LOG. The attribute options are specified as follows:

LOG(NONE)—nonrecoverable
Specifies the data set as nonrecoverable. CICS does not perform any logging of changes for a data set that has this attribute. Neither rollback nor forward recovery is provided.
LOG(UNDO)—recoverable
Specifies the data set as commit/rollback recoverable. CICS logs the before (UNDO) images of changes to the data set and backs out the changes if the application requests rollback or if the transaction terminates abnormally.
LOG(ALL)—recoverable
Specifies the data set as both commit/rollback recoverable and forward recoverable. In addition to the logging and recovery functions provided for LOG(UNDO), CICS logs the after (REDO) image of changes to the data set. The redo log records are used by forward recovery programs/products such as CICSVR (CICS VSAM recovery) to reconstruct the data set in the event of hardware or software damage to the data set.

You can specify VSAM recoverable data set attributes in IDCAMS (access method services) DEFINE and ALTER commands. In the data class, you can specify LOG along with BWO and LOGSTREAMID. If you want to be able to back up a data set while it is open, you should define them using the IDCAMS BWO(TYPECICS) parameter. Only a CICS application or DFSMStvs can open a recoverable data set for output because VSAM RLS does not provide the logging and other transactional functions required for writing to a recoverable data set.

When a data set is opened in a non-RLS access mode (NSR, LSR, or GSR), the recoverable attributes of the data set do not apply and are ignored. The recoverable data set rules have no impact on existing programs that do not use RLS access.