Cold start
Starting a system such as a CICS region without restoring its previous state, as opposed to a warm or emergency start.
Also written warm start, emergency start, initial start, START=AUTO, START=COLD
Systems like CICS and JES2 can restart in different ways, depending on how much of their previous state they bring back. The names are shared across products, though the details differ.
For CICS, the start type is chosen with the START parameter. An initial start begins from nothing, ignoring everything from the last run, including the logs. A cold start installs resources fresh from the CSD, and drops most of the recovery information for local resources. A warm start follows a normal shutdown and restores the region as it was. An emergency start follows a failure: CICS reads its log and backs out work that was in progress when it failed, so data stays consistent. START=AUTO lets CICS choose warm or emergency based on how it last ended.
JES2 has cold and warm starts too, and the difference matters even more. A JES2 cold start throws away every job and every piece of output on the spool, so it is very rare and carefully planned.
In conversation, a "cold start" means starting from a clean state. Before doing one on any system, check what will be lost.
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- CICS regionOne running copy of CICS, with its own programs, files and users. A site typically runs several.
- JES2The job entry subsystem: the part of z/OS that queues jobs, decides when they run, and collects their output.
- SITSystem initialization table: the set of start-up parameters that tells a CICS region how to run.
- CEDAThe CICS transaction used to define resources such as programs, transactions and files, and install them in a running CICS region.
- Commit and rollbackMaking a set of changes permanent together, or undoing them together, so a transaction never half-happens.