Misunderstood Coupling Facility Commands

(Originally posted 2008-05-03.)

I wonder how many of you recognise the terms “READ_COCLASS”, “WARM”, “RFCOM”,”WRITE_DATALIST” and “CASTOUT_DATALIST”.

Granted that in that list are two pairs of terms that I believe to be synonymous, but all five are relatively recent enhancements to Parallel Sysplex infrastructure that have a positive impact on DB2 Data Sharing performance (or at least the management of Performance).

As I mentioned in a previous post I’m going to Poughkeepsie soon to work on a Parallel Sysplex Performance Redbook – which will deal with topics such as “Data Sharing at a Distance” and “New Parallel Sysplex Technologies”. In preparation for this (not that I do much preparation for such things) I read through the various sections on Data Sharing Performance in the various DB2 Performance Topics Redbooks, starting at the beginning – with Version 4.

It might be significant that I don’t really understand these Coupling Facility commands. But then again it might not be… given that there are (without being self-deprecating) far better proponents of DB2 Data Sharing performance. In any case I feel the material that’s out there falls short in terms of describing when these commands are used and what benefit they bring (and what the downsides, if any, might be. So I hope to write some material in this area and ask (what I hope to be) searching questions of Development.

Now, these commands were first exploited by DB2 Versions 6 and 8. So the material might end up on the cutting-room floor. After all we’re all interested in System z10, CFLEVEL 15 and DB2 Version 9. Right? 🙂 What I’m hoping to do – in any case – is to share some of that material through this blog. If I succeed in doing that I hope you’ll help me by feeding back on the blog entries. Corrections, additional questions, etc.

And the fun really begins on May 22nd. Just after UKCMG.

Published by Martin Packer

I'm a mainframe performance guy and have been for the past 35 years. But I play with lots of other technologies as well.

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