Forward recovery of CICS data sets

CICS® supports forward recovery of VSAM data sets updated by CICS file control (that is, by files or CICS-maintained data tables defined by a CICS file definition).

CICS writes the after-images of changes made to a data set to a forward recovery log, which is a general log stream managed by the MVS system logger.

CICS obtains the log stream name of a VSAM forward recovery log in one of two ways:
  1. For files opened in VSAM record level sharing (RLS) mode, the explicit log stream name is obtained directly from the VSAM ICF catalog entry for the data set.
  2. For files in non-RLS mode, the log stream name is derived from:
    • The VSAM ICF catalog entry for the data set if it is defined there, and if RLS=YES is specified as a system initialization parameter. In this case, CICS file control manages writes to the log stream directly.
    • A journal model definition referenced by a forward recovery journal name specified in the file resource definition.

      Forward recovery journal names are of the form DFHJnn where nn is a number in the range 1–99 and is obtained from the forward recovery log id (FWDRECOVLOG) in the FILE resource definition.

      In this case, CICS creates a journal entry for the forward recovery log, which can be mapped by a JOURNALMODEL resource definition. Although this method enables user application programs to reference the log, and write user journal records to it, you are recommended not to do so. You should ensure that forward recovery log streams are reserved for forward recovery data only.

Note: You cannot use a CICS system log stream as a forward recovery log.

The VSAM recovery options or the CICS file control recovery options that you require to implement forward recovery are explained further in Defining files as recoverable resources.

For details of procedures for performing forward recovery, see Forward recovery procedures.

Forward recovery for non-VSAM resources

CICS does not provide forward recovery logging for non-VSAM resources, such as BDAM files. However, you can provide this support yourself by ensuring that the necessary information is logged to a suitable log stream. In the case of BDAM files, you can use the CICS autojournaling facility to write the necessary after-images to a log stream.