Tuesday, 25 September 2007

Getting the most out of CICS

CICS has been around for a long time and has seen an enormous number of changes over the years. And that’s the reason it is still in constant use at so many Fortune 500 companies. It’s re-invented itself and kept up with computing trends, but never lost its overall reliability.

Optimizing its performance has been on the mind of CICS systems programmers since day 1. In this blog, I’d like to pass on two hints and tips that I’ve recently received.

The first one is to ensure that all exits etc are threadsafe and defined as such, so that OPENAPI TRUEs, such as DB2, can be exploited efficiently using OTE (Open Transaction Environment), the dynamic plan exit, for example, and the XRMIIN and XRMIOUT GLUEs. This is to avoid TCB switching, which will have an adverse effect on performance. Readers might like to take a look at the recently updated redbook on threadsafety in CICS.

The second tip is about WS-Security, and it really says, use WS-Security only if it is what you need! It’s worth remembering that the performance impact of using WS-Security to secure Web services is not insignificant. Therefore, if SSL (point-to-point) security is adequate, then use it rather than WS-Security because performance will be better! Also, if all you require is a simple username/password check, then it is better to implement this via a handler program in the pipeline rather than using the WS-Security solution. So, think about what security you really want – in many situations, WS-Security is not what is required and better performing alternatives probably exist.

Talking about CICS (hopefully) gives me the opportunity to mention Xephon’s CICS Update (
www.xephonusa.com). If you have something to say about CICS, a simple hint and tip, or you have recently completed a project that is worth sharing (the mistakes and the successes), or you’ve tested software that runs with CICS and identified its strengths and weaknesses, or even CICS performance tips, then contact the editor (TrevorE@xephon.com). Articles from new contributors are always welcome.

My thanks to Andy Wright and Darren Beard from Hursley for their CICS tips.

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