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jim haire · Beginner Joined: 30 Dec 2002 Posts: 140 Topics: 40

Our shop is going to be moving to COBOL version 5 in the near future. There has been some initial research done testing some of the new features, but the major concern is what the CPU Impact will be during execution.

2 questions:
a. What has your experience been when your shop has moved to
COBOL version 5 in regards to CPU times when executing a program?

b. Do you use the OPTIMIZE(FULL) parm for compiling and if you do
have you seen any CPU performance reduction from that?

kolusu · Posted: Thu Jan 28, 2016 10:39 am Post subject:

jim haire,

Please check out the presentation by Tom Ross which talks about performance and several optimizing parameters

http://www.ibm.com/support/docview.wss?uid=swg27039561&aid=1
_________________
Kolusu
www.linkedin.com/in/kolusu

William Collins · Supermod Joined: 03 Jun 2012 Posts: 437 Topics: 0

Up to V4, the only difference between OPT(STD) and OPT(FULL) is that FULL checks for unreferenced data-items (individual 01-levels, group 01-levels and 77-levels) and excludes them from the the generation of storage.

V5 has three levels of optimisation, 0, 1 and 2. That is correct, even level 0 does some straightforward optimisation, there is no way of getting a program with no optimisation at all using V5.

The higher the optimisation level you use, the longer a compile can take, and the more the generated code should benefit from a reduction in CPU usage.

The redundant storage removal is now done by a separate compiler option.

Optimised programs may tend to be somewhat larger. You should see performance improvements, but of what scale depends on your systems, not on anyone else's.

If going to V5, go to V5.2. There are several new options and features, and more in V5.2 than in V5.1. Make sure all fixes are applied.

Migrating to V5 is a much larger task than, say, from V3 to V4. The entire code-generation and optimisation are new.

V5 will use z/Architecture instructions (from ARCH level 7 through to 11, which latter is the z13). V4 only generates for ESA.

jim haire · Beginner Joined: 30 Dec 2002 Posts: 140 Topics: 40

Thanks Kolusu and William for your responses. Good information!

We'll experiment with these.