Better Routing of DDF Work in a Parallel Sysplex with z/OS 1.7

(Originally posted 2006-01-12.)

I’m working through the queue of interesting APARs that have been sitting in my in-basket. (I guess it’s a “New Year’s tidying up” thing.) 🙂 Here’s one that relates to workload routing for DDF. It does prereq z/OS R.7 on all members so it won’t be of that much interest to customers right now…

APAR PK03045 “DB2 z/OS support for z/OS 1.7 WLM routing service” describes the DB2 enhancement to support this new routing algorithm. This is available for both DB2 Version 7 and Version 8.

In a nutshell the “old” WLM algorithm used to provide routing recommendations to interested clients based on available CPU capacity. However that didn’t take into account anything else that within DB2 that might cause a particular Data Sharing Group Member to be a poor placement choice. DB2 has been changed to ensure that WLM has accurate information about the delay, or queue, time of any of the enclaves that DB2 DDF created and used to perform its work requests. Recall: in-bound DDF work acquires an enclave when it goes through the initialisation process in the DIST address space, prior to executing SQL.

This enhancement advances the state of the art when it comes to workload balancing – a topic that has recently exercised my brain more than it had in the past. I would be interested in hearing of customers’ experiences in this area, whether DB2 or not.