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:
- 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.
- 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).
- 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.
- 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.