March 10, 2009
 |
- Welcome to Cheryl's List!
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- 1. Cheryl’s Presentations
at SHARE
2. Caution For RSU0901
3. Important z/OS 1.10 APAR
Cheryl's presentations from last week's Austin SHARE conference are now available at http://www.watsonwalker.com/presentations.html. These are:
Session
3117 - Can You Teach a New Capacity & Performance Specialist Old Tricks?
Session
2509 - Cheryl's Hot Flashes # 21
Almost all of the SHARE presentations for this conference are now available on the SHARE Web site at www.share.org by clicking 'Proceedings'. They should be available to the public until (about) the end of July.
2. Caution With RSU0901
Our many thanks go to Ed Webb of SAS Institute for this timely warning. Most installations are preparing to install RSU0901, the most current z/OS combined mainte-nance. Although IBM provides a warning about one of the PTFs in this RSU, their warning may not prepare you well enough.
The Language Environment (LE) PTF UK41392 (fixing a PE PTF) contains an ACTION HOLD warning about high CPU usage during the apply. On Ed’s system (a z9-BC R02), the apply took 45 minutes of CPU time and produced 14 million lines of output to SYSPRINT!
The PTF appears to relink the entire LE component. More information can be found in APARs PK75057 (3Dec2008) and PK73828 (29Oct2008). Just be prepared.
3. Important z/OS 1.10 APAR
In order to improve DB2 performance, IBM changed the logic for obtaining storage with GETMAIN STORAGE OBTAIN in z/OS 1.10. Read the APAR below for a more detailed explanation of the situation. But essentially, getmains of less than 4096 bytes are now allocated in such a way that the storage might not be zeroes. While the method follows the rules for storage allocation (i.e. only getmains of 4K on a Page Boundary and getmains of over 8K are cleared first), some ISVs and applications threw up on z/OS 1.10 because they assumed the area would be clear. As you can imagine, having authorized programs pick up a leftover field and assume it’s a valid address could lead to abends which are exceedingly difficult to diagnose.
In order to help installations who might have these errant programs, IBM is providing APAR OA27291 (z/OS 1.10, 4Feb2009) that changes the default behavior to match that of z/OS 1.9. If you apply the PTF and have a large DB2 site that runs at high CPU utilization, you can obtain the performance improvement by coding an override in the DIAGxx member (VSM USEZOSV1R9RULES(NO)). YES (to use the z/OS 1.9 behavior is the default after the PTF is applied). It’s particularly important to find out if your ISVs have any fixes for this particular situation.
Stay Tuned!
Cheryl Watson
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