Starting CICS with the START=COLD parameter

START=COLD performs a dual type of startup, performing a cold start for all local resources while preserving recovery information that relates to remote systems or resource managers connected through the resource manager interface (RMI).

This ensures the integrity of the CICS® region with its partners in a network that manages a distributed workload. You can use a cold start to install resource definitions from the CICS system definition data set (CSD) and from macro control tables. It is normally safe to perform a cold start for a CICS region that does not own any local resources (such as a terminal-owning region that performs only transaction routing). For more information about performing a cold start, and when it is safe to do so, see Initial and cold starts .

If you specify START=COLD, CICS either discards or preserves information in the system log and global catalog data set, as follows:
  • CICS deletes all cataloged resource definitions in the CICS catalogs and installs definitions either from the CSD or from macro control tables. CICS writes a record of each definition in the global catalog data set as each resource definition is installed. All transaction and transaction class resource definitions, journal model definitions, programs, mapsets, and partitionsets are installed from the CSD, and are cataloged in the global catalog. Journal name definitions (including the system logs DFHLOG and DFHSHUNT) are created using the installed journal models and cataloged in the global catalog.

    If resource definition overrides support is in use, resource overrides are applied to relevant resources when those resources are installed. See Overriding resource definitions.

  • Any program LIBRARY definitions that had been dynamically defined will be lost. Only the static DFHRPL concatenation will remain, together with any LIBRARY definitions in the grouplist specified at startup or installed via BAS at startup.
  • CICS preserves the recovery manager control record, which contains the CICS logname token used in the previous run. CICS also preserves the log stream name of the system log.
  • CICS discards any information from the system log that relates to local resources, and resets the system log to begin writing at the start of the primary log stream.
    Note: If CICS detects that there were shunted units of work at the previous shutdown (that is, it had issued message DFHRM0203) CICS issues a warning message, DFHRM0154, to let you know that local recovery data has been lost, and initialization continues. The only way to avoid this loss of data from the system log is not to perform a cold start after CICS has issued DFHRM0203.

    If the cold start is being performed following a shutdown that issued message DFHRM0204, CICS issues message DFHRM0156 to confirm that the cold start has not caused any loss of local recovery data.

  • CICS releases all retained locks:
    • CICS requests the SMSVSAM server, if connected, to release all RLS retained locks.
    • CICS does not rebuild the non-RLS retained locks.
  • CICS requests the SMSVSAM server to clear the RLS sharing control status for the region.
  • CICS does not restore the dump table, which may contain entries controlling system and transaction dumps.
  • CICS preserves resynchronization information about distributed units of work—information regarding unit of work obligations to remote systems, or to non-CICS resource managers (such as Db2®) connected through the RMI. For example, the preserved information includes data about the outcome of distributed UOWs that is needed to allow remote systems (or RMI resource managers) to resynchronize their resources.
    Note: The system log information preserved does not include before-images of any file control data updated by a distributed unit of work. Any changes made to local file resources are not backed out, and by freeing all locks they are effectively committed. To preserve data integrity, perform a warm or emergency restart using START=AUTO.
  • CICS retrieves its logname token from the recovery manager control record for use in the exchange lognames process during reconnection to partner systems. Thus, by using the logname token from the previous execution, CICS ensures a warm start of those connections for which there is outstanding resynchronization work.

To perform these actions on a cold start, CICS needs the contents of the catalog data sets and the system log from a previous run. The CICS log manager retrieves the system log stream name from the global catalog ensuring CICS uses the same log stream as on a previous run.

See Reusing the global catalog to perform a cold start for details of the actions that CICS takes for START=COLD in conjunction with various states of the global catalog and the system log.

The recovery manager utility program DFHRMUTL returns information about the type of previous CICS shutdown which is of use in determining whether a cold restart is possible or not.

The following information provides more detail about what happens to different CICS resources when you perform a cold start. This information applies to resources stored in the CSD and macro control tables. Resources that are defined in CICS bundles are not stored in the CSD, and they are recovered using different processes, depending on whether the CICS bundles were created from a definition or by platforms and applications. For details of how CICS handles BUNDLE resources at startup, see Recovery of resources in bundles.