ABCs of z/OS System Programming Volume 3 - IBM Redbooks

7.10 VSAM RLS/CICS data set recovery
Recoverable data sets
Defined as LOG(UNDO/ALL) in the catalog
Figure 7-10 Recoverable data sets
Recoverable data set
VSAM record-level sharing introduces a VSAM data set attribute called LOG. With this
attribute a data set can be defined as recoverable or non-recoverable. A data set whose log
parameter is undefined or NONE is considered non-recoverable. A data set whose log
parameter is UNDO or ALL is considered recoverable. For recoverable data sets, a log of
changed records is maintained to commit and back out transaction changes to a data set.
A data set is considered recoverable if the LOG attribute has one of the following values:
► UNDO
The data set is backward recoverable. Changes made by a transaction that does not
succeed (no commit was done) are backed out. CICS provides the transactional recovery.
See also 7.11, “Transactional recovery” on page 394.
► ALL
The data set is both backward and forward recoverable. In addition to the logging and
recovery functions provided for backout (transactional recovery), CICS records the image
of changes to the data set, after they were made. The forward recovery log records are
used by forward recovery programs and products such as CICS VSAM Recovery
(CICSVR) to reconstruct the data set in the event of hardware or software damage to the
data set. This is referred to as data set recovery. For LOG(ALL) data sets, both types of
recovery are provided, transactional recovery and data set recovery.
392 ABCs of z/OS System Programming Volume 3
UNDO - backout logging performed by CICS
ALL - both backout and forward recovery logging
LOG(ALL) data sets must have a
LOGSTREAMID(forwardrecoverylog) also defined in
the catalog
Non-recoverable data sets
Defined as LOG(NONE) in the catalog
No logging performed by CICS