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user exit program to request a CICS abend, and thereby initiate a takeover,
and for the overseer program to issue the PERFORM TAKEOVER command
while acting on the same information.
– At particular times of the day, perhaps when fewer operational staff are
available than at other times, you may find it convenient to change the
TAKEOVER setting for some, or all, of your regions. For example, you can
change the TAKEOVER value for a region from COMMAND or MANUAL to
AUTO, without shutting down the alternate, so that takeover is automatic until
the setting is next changed. The CEBT command is as follows:
MODIFY jobname,CEBT SET TAKEOVER AUTO
In both of these examples, you would include takeover commands in the
command list tables (CLTs) of these regions to ensure that their related regions
are also switched when appropriate.
There is one optional section of code in the overseer program, which is described
below.
Loop or wait detection
The sample overseer program includes some code that you can use to detect
possible loops or waits in the active CICS region.
The sample program monitors the CICS task control block (TCB) time stamp. If this
remains the same for a period defined by the variable LOOPTM, a message is sent
to the console warning of a possible loop or wait. The value of LOOPTM is the
number of seconds (wait time) before a loop is suspected, and may need to be
changed to suit your requirements and to avoid the detection of “false” loops. It
should be set to a value greater than the largest runaway task time interval (as
specified on the ICVR system initialization parameter) to avoid detection of user
transaction loops.
To include this LOOP WARNING code, set the variable &LOOPWARN to ‘1’ and
reassemble the sample.
Assembling and link-editing the overseer program
The non-specific job control statements required to assemble and link-edit the
overseer program are the same as those required for user-replaceable programs,
and are described in “Assembling and link-editing user-replaceable programs” on
page 436.
The specific link-edit statements that you require are:
ORDER DFH$AXRO this CSECT is in USERTEXT(DFH$AXRO)
ORDER DFH$AGCB this CSECT is in DLOADLIB(DFH$AGCB)
ORDER DFH$ARES this CSECT is in DLOADLIB(DFH$ARES)
ORDER DFH$ADSP this CSECT is in DLOADLIB(DFH$ADSP)
INCLUDE USERTEXT(DFH$AXRO)
INCLUDE DLOADLIB(DFH$ADSP)
INCLUDE DLOADLIB(DFH$AGCB)
INCLUDE DLOADLIB(DFH$ARES)
ENTRY DFHXRONA
NAME DFH$AXRO(R)
If you change the overseer code in any way, note that the libraries
SYS1.SDFHMAC and SYS1.AMODGEN are required for the assembly, and that the
Chapter 26. The extended recovery facility overseer program 705