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to be started, and they cannot communicate with terminals. Further, second phase
PLT programs must not cause any resource security checking or DB2 calls to be
performed.
If a transaction abend occurs while the PLTSD program is running, CICS is left in a
permanent wait state. To avoid this happening, ensure that your PLTSD program
handles all abend conditions.
The second quiesce stage is complete when all of the second phase PLT programs
have been executed.
You cannot use Debug Tool to debug a PLT program during the second queisce
stage.
The shutdown assist utility program, DFHCESD
CICS provides a shutdown assist transaction, that can be run during the first
quiesce stage of shutdown. It can be run on a normal or an immediate shutdown.
You specify the name of the shutdown transaction on the SDTRAN system
initialization parameter, or on the SDTRAN option of the PERFORM SHUTDOWN
and PERFORM SHUTDOWN IMMEDIATE commands. You can also specify that no
shutdown assist transaction is to be run. If you do specify that no shutdown assist
transaction is to be run:
v On a normal shutdown, CICS waits for all running tasks to finish before entering
the second stage of quiesce. Long running or conversational transactions can
cause an unacceptable delay or require operator intervention.
v On an immediate shutdown, CICS does not allow running tasks to finish and
backout is not performed until emergency restart. This can cause an
unacceptable number of units of work to be shunted, and locks to be retained
unnecessarily.
The purpose of the shutdown assist transaction is to help solve these problems;
that is, to ensure that as many tasks as possible commit or back out cleanly within
a reasonable time.
The default shutdown assist transaction is CESD, which starts the CICS-supplied
program DFHCESD. DFHCESD attempts to purge and back out long-running tasks
using increasingly stronger techniques. It ensures that as many tasks as possible
commit or back out cleanly, enabling CICS to shut down in a controlled manner. For
information about DFHCESD, and about how to write your own shutdown assist
transaction, see the CICS Operations and Utilities Guide.
General considerations when writing initialization and shutdown
programs
v It is recommended that you terminate all PLT programs with an EXEC CICS
RETURN command.
v PLT programs receive control in primary-space translation mode. For information
about translation modes, see the IBM ESA/390 Principles of Operation manual.
They must return control to CICS in the same mode, and must restore any
general purpose registers or access registers that they use.
v All PLTPI programs run under the CICS internal transaction name CPLT.
Therefore, because CICS internal transactions are defined with the WAIT indoubt
attribute set to 'YES', an in-doubt failure that occurs while running a PLTPI
Chapter 4. Writing initialization and shutdown programs 429