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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.
Although the CICS system log is logically a single logical log stream, it is written
to two physical log streams—a primary and a secondary. In general, it is not
necessary to distinguish between these, and most references are to the system log
stream. Using a primary and a secondary log stream for its single system log
enables CICS to optimize its use of log stream storage through its process of
moving long-running UOWs from the primary to secondary logstreams.
Specifying a JOURNALMODEL resource definition
During a cold start, and a warm and emergency restart, CICS retrieves the names
of its system log streams from the global catalog, ensuring that it reconnects to the
same log streams that were used on the previous run.
During an initial start, CICS uses default log stream names, unless you specify
otherwise on a JOURNALMODEL resource definition. The process of selecting and
connecting to a system log stream is as follows:
Without a JOURNALMODEL definition
If CICS can't find a JOURNALMODEL resource definition for DFHLOG and
DFHSHUNT, it issues calls to the MVS system logger to connect to its system
log streams using default names. These are:
region_userid.applid.DFHLOG
region_userid.applid.DFHSHUNT
where region_userid is the RACF
®
user ID under which the CICS address space
is running, and applid is the region's VTAM APPL name (taken from the
APPLID system initialization parameter). The CICS-supplied
JOURNALMODEL definitions for default DFHLOG and DFHSHUNT log
streams are in the CSD group DFHLGMOD, which is included in DFHLIST.
If you use these default log stream names, ensure that
v The default log streams are defined explicitly to the MVS system logger, or
v Suitable model log streams are defined for dynamic creation.
With a JOURNALMODEL definition
If CICS finds a JOURNALMODEL definition with JOURNALNAME(DFHLOG)
and JOURNALNAME(DFHSHUNT), it issues calls to the MVS system logger
to connect to the system log streams named in the definitions. Ensure that the
system log stream names are unique to the CICS region.
If you define JOURNALMODEL resource definitions for your system logs,
ensure that:
v The log streams named in the JOURNALMODEL are defined to the MVS
system logger, or
v Suitable model log streams are defined that enable them to be created
dynamically.
If you don't want to use a system log (for example, in a CICS test region), specify
JOURNALMODEL resource definitions for DFHLOG and DFHSHUNT with
TYPE(DUMMY). Note that running CICS with the system log defined as
TYPE(DUMMY) forces you to perform an initial start, and CICS does not support
dynamic transaction backout.
Chapter 11. Defining system and general log streams 109