Sanjay Rajput, Syntel Inc 2
COBOL Tuning: Parameter selection
Did you know that your selection of both COBOL compiler options and run-time options can
have significant impacts on run-time performance? Selecting appropriate parameters can boost
your run-time performance up to 35%.
This article provides a summary of the details contained within the IBM document. You would
find this to be a standard document across all the performance tuning papers as it originates from
the IBM document but nevertheless we would just go through the details once and for all to get
comfortable across this COBOL domain.
The selection of specific compiler options can have a cumulative negative impact of over 35% in
run-time performance. These selections have been found to be far and away the cause of
performance issues within the COBOL arena. The options that will be discussed cause both
excessive path-length (cycles burned) and unnecessary I/O.
Compiler Options Causing Performance Issues
ARITH (Extend/Compat) - Use of the ARITH option, EXTEND, can cause and average 1%
performance impact. This option led to a worse case execution time 38% slower then when using
the COMPAT parameter.
AWO(Apply Write-Only) – Use of this option for cause Apply Write-Only to be forced for all
variable-length, blocked sequential files. One benchmarked program showed a 88% reduction in
run-time when this option was removed. This can cause up to a 98% reduction in I/O to process
DATA (24/31) – Use of this option determines where Working-Storage and FD Record areas
will reside. While no benchmark data was collected to substantiate one choice over the other, the
logical choice would be DATA (31) if the user needs to relieve storage constraints below the 16-
DYNAM/NODYNAM – Use of this option determines if dynamic or static cal