CICS® uses two catalog data sets:
The CICS System Definition Guide tells you how to create and initialize these CICS catalog data sets.
While CICS is running, the catalogs (and the system log) receive information passed from one execution of CICS, through a shutdown, to the next execution of CICS. This information is used for warm and emergency restarts, and to a lesser extent for cold starts also. If the global catalog fails (for reasons other than filling the available space), the recovery manager control record is lost. Without this, it is impossible to perform a warm, emergency, or cold start, and the only possibility is then an initial start. For example, if the failure is due to an I/O error, you can’t restart.
Usually, if the global catalog fills, CICS abnormally terminates, in which case you could define more space and attempt an emergency restart.
Consider putting the catalog data sets on the most reliable DASD available--RAID or dual-copy devices--to ensure maximum protection of the data. Taking ordinary copies is not recommended because of the risk of getting out of step with the system log.
From a restart point of view, the system log and the CICS catalog (both data sets) form one logical set of data, and all of them are required for a restart.
The global catalog contains information needed at restart, and CICS uses it to store the following information:
Most resource managers update the catalog whenever they make a change to their table entries. Terminal and profile resource definitions are exceptions (see the next list item about the catalog warm keypoint). Because of the typical volume of changes, terminal control does not update the catalog, except when:
All this information is essential for a successful restart following any kind of shutdown.
The CICS local catalog data set represents just one part of the CICS catalog, which is implemented as two physical data sets. The two data sets are logically one set of cataloged data managed by the CICS catalog domain. Although minor in terms of the volume of information recorded on it, the local catalog is of equal importance with the global catalog, and the data should be equally protected when restarts are performed.
If you ever need to redefine and reinitialize the CICS local catalog, you should also reinitialize the global catalog. After reinitializing both catalog data sets, you must perform an initial start.
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