Chapter 6. Transaction manager performance 127
For monitoring, you can obtain the overall time for the above activities. The number of I/Os
should be checked periodically.
7. Message queue GU
This is the GU call to the message queue. It is chosen as a measuring point because the
event is recorded on the system log and is used as a starting point for iterations of
processing when more than one message is serviced at a single scheduling of the
program. Program control can now be considered effectively passed from IMS to the
application.
6.2 Program load options
The following load options can affect performance:
򐂰 COBOL options:
LIBKEEP (causes the run-time library routines to remain in memory)
RESIDENT (requests library routines be located dynamically at run time, not
link-edited)
RENT (program is re-entrant)
NODYNAM (no dynamic calls)
򐂰 DBLDL is a parameter (default 20, maximum 9999) in the EXEC statement of the
DFSMPR procedure that maintains a list of BLDL entries in the dependent region
containing the directory index for programs. It is maintained on a most active, most
recently used basis, and reduces the I/O to the program directory. Programs with entries in
this list have a lower schedule to first DL/I call elapsed time than infrequently used
programs.
For a region that is used to test new or changed programs, set the DBLDL parameter to 0,
ensuring that the most current version of the program is loaded for each execution.
Specifying the DOPT parameter disables quick reschedule.
򐂰 LLA is the recommended method for managing dynamically loaded program libraries. For
IMS application programs, it saves load modules in a data space, so that the modules can
be retrieved more efficiently than through DASD. LLA monitors the frequency with which
modules are accessed and readjusts its data space population to optimize the probability
of having a module in the data space when it is requested.
򐂰 LRR (Library Routine Retention) is an LE function that provides a performance
improvement for those applications or subsystems with the following attributes:
The application or subsystem invokes programs that require Language Environment®.
The application or subsystem is not Language Environment-conforming. That is,
Language Environment is not already initialized when the application or subsystem
invokes programs that require Language Environment.
The application or subsystem, while running under the same task, repeatedly invokes
programs that require Language Environment.
The application or subsystem is not using Language Environment preinitialization
services.

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