Initial and cold starts

This section describes functions to manage the exceptional conditions that can occur in a transaction-processing network when one system performs an initial or cold start.

Important:
  • Except where otherwise stated, this section describes the effect of initial and cold starts on CICS® Transaction Server for z/OS® systems that are connected by MRO, IPIC, or ISC over SNA (APPC) parallel-session links. For information about the effects when other connections are used, see Connections that do not fully support shunting.
  • In the rest of this section, the term cold start means a cold start in the CICS TS for z/OS meaning of the phrase (see cold start section). Where an initial start is intended, the term is used explicitly.

CICS Transaction Server for z/OS systems can be started without full recovery in two ways:

Initial start
An initial start can be performed in either of the following circumstances:
  • INITIAL is specified on the START system initialization parameter.
  • AUTO is specified on the START system initialization parameter, and the recovery manager utility program, DFHRMUTL, has been used to set the AUTOINIT autostart override in the global catalog.

On an initial start, all information about both local and remote resources is erased, and all resource definitions are reinstalled from the CSD or from CICS tables.

An initial start should be performed only in exceptional circumstances. Examples of times when an initial start is appropriate are:
  • When bringing up a new CICS system for the first time
  • After a serious software failure, when the global catalog or system log has been corrupted.
Cold start
A cold start can be performed in either of the following circumstances:
  • COLD is specified on the START system initialization parameter.
  • AUTO is specified on the START system initialization parameter, and the DFHRMUTL utility has been used to set the AUTOCOLD autostart override in the global catalog.

In CICS TS for z/OS, a cold start means that log information about local resources is erased, and resource definitions are reinstalled from the CSD or from CICS tables. However, resynchronization information relating to remote systems or to RMI-connected resource managers is preserved. The CICS log is scanned during startup, and information regarding unit of work obligations to remote systems, or to non-CICS resource managers (such as DB2®) connected through the RMI, is preserved. (That is, any decisions about the outcome of local UOWs, needed to allow remote systems or RMI resource managers to resynchronize their resources, are preserved.)

For guidance information about the different ways in which CICS can be started, see Troubleshooting for recovery processing.