Defining system log streams

You must define a system log if you want to preserve data integrity in the event of unit of work failures and CICS® failures.

A system log is mandatory for the following situations:
  • The backout of recoverable resources changed by failed units of work.
  • Cold starts, to enable CICS® to restore units of work that were shunted at the time of the shutdown.
  • Warm restarts, to enable CICS® to restore the region to its state at the previous shutdown, including units of work that were shunted at the time of the shutdown.
  • Emergency restarts, to enable CICS® to perform the following tasks:
    • Restore the region to its state at the previous shutdown, including units of work that were shunted at the time of the shutdown.
    • Recover units of work that were in-flight at the time of the CICS® failure and perform backout of recoverable resources that were updated before the failure.

CICS® log manager connects to its log stream automatically during system initialization, unless it is defined as TYPE(DUMMY) in a CICS® JOURNALMODEL resource definition.