Running efficiently with CICS, IMS, or VSAM
You can improve performance for online programs running under CICS® or IMS, or programs that use VSAM, by following these tips.
CICS: If
your application runs under CICS,
convert EXEC CICS LINK
commands to COBOL CALL
statements
to improve transaction response time.
IMS: If your application runs under IMS, preloading the application program and the library routines can help reduce the overhead of loading and searching. It can also reduce the input-output activity.
For better system performance, use
the RENT
compiler option and preload the applications
and library routines when possible. You can also use the Language Environment® library routine retention
(LRR) function to improve performance in IMS/TM regions.
VSAM: When you use VSAM files,
increase the number of data buffers for sequential access or index
buffers for random access. Also, select a control interval size (CISZ
)
that is appropriate for the application. A smaller CISZ
results
in faster retrieval for random processing at the expense of inserts.
A larger CISZ
is more efficient for sequential processing.
For
better performance, access the records sequentially and avoid using
multiple alternate indexes when possible. If you use alternate indexes,
access method services builds them more efficiently than the AIXBLD
runtime
option.
Coding COBOL programs to run under CICS
Developing COBOL programs for IMS
Improving VSAM performance
Language Environment Customization
Language Environment Programming Guide (Specifying runtime options)