Life cycle of a CICS region

This topic gives an overview of what happens during the startup and shutdown of a CICS® region. It is based on a region that is predefined in the CICS permanent database.

When a CICS region is started, the following actions occur:
  1. The CICS region main process is created. The initialization actions of the main process depend on whether you requested a cold or an automatic (auto) startup.
    In a cold start, the startup of the region occurs without regard to any previous region activity. CICS installs the permanent resource definitions into the autostart and runtime databases. For an automatic startup, CICS starts the region according to its state at the last shutdown. This results in either of the following conditions:
    • A cold start, if you have not started the region before. When a region is cold started, CICS installs (copies) the permanent definitions into the autostart and runtime databases. While running, a CICS region can use the resources that are defined in the runtime database. For more information, see Cold starts and warm starts and Cold starting the SFS server.
    • A warm start, if the region terminated with a normal shutdown. When a region is warm started, the permanent database is not copied into the two databases. Instead, CICS uses the definitions from the previous CICS instance (already in the autostart database, which represents the last state of the runtime definitions). For more information, see Cold starts and warm starts.
    • An emergency restart, if the region terminated with an immediate shutdown or abnormally. When a CICS region performs an emergency restart, CICS also uses the definitions in the autostart database. It also performs recovery processing as summarized in Recovery during restart.

    The main process also obtains the operating system memory that it needs.

  2. The main process starts the RPC listener and, if the system was predefined appropriately, one or more TCP/IP listeners, the SNA listener, and the named-pipe listener (used for local 3270 terminals on Windows only).
  3. The main process creates the following management processes:
    • The log manager, which opens the system log and waits for a request to write the first checkpoint.
    • The application manager, which creates the minimum number of application servers that is predefined in the region definition. It maintains this minimum number while the CICS region is running.
    • The time service starts itself and waits for the first timed request.
  4. The CICS region runs some internal CICS transactions and writes a checkpoint to the system log.

The CICS region is now started and can run user transactions. If any errors occur during startup, the system generates an error message so that appropriate action can be taken.