Cold start

A cold start is required only when you first initialize IMS or after changing the nucleus during a system definition. You must also cold start IMS after scratching and reallocating shared-message-queue structures if these structures contained messages.

Request a cold start using the /NRESTART CHECKPOINT 0 or /ERESTART COLDSYS command. When you specify the COLDSYS keyword, the /ERESTART command initiates a cold start, not an emergency restart.

Note that if AUTO=Y is specified in the startup procedure, you cannot cold start IMS or modify any restart options before IMS automatically executes either an emergency restart or warm restart, as determined by the circumstances of the prior termination.

In a non-shared-queues environment, a cold start assumes empty message queues: if any messages exist, IMS discards them. In a shared-queues environment, IMS does not discard messages on shared queues during a cold start. If any affinities exist for VTAM® generic resource groups, IMS deletes them. IMS never uses information from a previous shutdown as input to a cold start.

Optionally, you can format the IMS message queue data sets, WADS, and restart data set (RDS) during a cold restart. During a cold start, IMS loads all control blocks from the system libraries.

In a shared-queues environment, any locked messages remain locked after the IMS cold start until IMS (or other Common Queue Server client) unlocks or deletes them.

IMS systems that use dynamic resource definition (DRD) can store resource definitions for application programs, databases, Fast Path routing codes, and transactions in a resource definition data set (RDDS) or the IMSRSC repository. During a cold start, IMS can be set up to automatically import the stored resource and descriptor definitions. If your IMS system is not configured to automatically import the resource definitions, you can issue the IMPORT command after the restart process is complete. The IMPORT command, as well as all of the other type-2 dynamic resource definition commands, require that the SCI and OM CSL components are started.

In order to recover changes to the runtime resource definitions across a cold start, you must export the resource definitions to an RDDS or the IMSRSC repository while IMS is up. If you do not, any changes made to resources and descriptors in the online system might be lost.

If the IMS resource definitions were not exported to the IMSRSC repository and IMS had to perform a cold start, you can create a non-system from RDDS from the IMS log using the DFSURCL0 utility with EXPORTNEEDED parameter. If such an RDDS was created then you can specify that RDDS on the IMPORT command after the cold start is complete.

During a cold start, the partition status or access state will be copied from the HALDB master. If you export the HALDB master status to the RDDS or the repository, the status of the master and its partitions will be obtained from the RDDS or the repository.

If an error occurs while trying to access an RDDS during the automatic import process, automatic import terminates abnormally. IMS either continues with the cold start process without any runtime resource definitions defined, or IMS stops the cold start process. If an error occurs during automatic import processing because of an invalid resource or descriptor definition, one of the following situations occurs:
  • Automatic import processing terminates abnormally, and IMS cold start terminates abnormally with a U3397 abend.
  • Automatic import processing continues, and the resource in error is marked and given a not-initiated status (NOTINIT).

The action IMS takes depends on the values specified for the RDDSERR and the IMPORTERR parameters in the DFSDFxxx member.