Using more memory in DB2 V8 running on z/OS 1.7 can still be a net
positive.
There are some things you can set in IEAOPTxx to reduce overhead.
z/OS 1.8 is the real solution for handling large memory more efficiently
in z/OS but the benefits of large buffer pools with DB2 V8 are pretty
significant.
/* */
/* SRM INVOCATION INTERVAL CONSTANT */
/* SET TO 3K PER LOCAL FIX FOR OA18452 TILL CLOSURE... SJK MAR-08-07 */
/* WAS 1K */
RMPTTOM=3000,
/* */
/* UICFRAMESCHECKTIME is the number of frames (in thousands) that */
/* RSM processes on one address space queue before checking for the */
/* RSM timeout value which is internally defaulted at 25ms. While */
/* the system is running address space queues to do UIC updating the */
/* RSM lock is held. Other callers who need this lock (such as to do */
/* a page fix to do DB2 I/O, or assigning a frame) will spin waiting */
/* for the address space queue to be processed. The default */
/* UICFRAMESCHECKTIME is 525 (2GB). */
/* */
/* Set to 5 per IBM WSC ... SJK JUL-18-07 */
UICFRAMESCHECKTIME=5
The support for UICFRAMESCHECKTIME was provided with APAR OA07055 which
can be reviewed for additional information.
YMMV so do your own research and testing and consider consulting IBM if
you think you really have a problem this may help. I wouldn't suggest
you go making changes to IEAOPTxx to add either RMPTTOM or
UICFRAMESCHECKTIME if you are happy with your current z/OS 1.7 system.
Best Regards,
Sam Knutson, GEICO
System z Performance and Availability Management
mailto:[EMAIL PROTECTED]
(office) 301.986.3574
"Think big, act bold, start simple, grow fast..."
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On
Behalf Of Veilleux, Jon L
Sent: Wednesday, November 07, 2007 9:49 AM
To: IBM-MAIN@BAMA.UA.EDU
Subject: Re: Real storage usage - a quick question
In z/OS 1.8 the memory management is much more conducive to large
memory. They no longer use the least recently used algorithm and no
longer check every page. This has made a big difference for us. Under
1.7 we had issues with large real memory sizes due to the constant
checking by RSM. This is no longer the case and we have increased our
memory dramatically with no performance hit.
Jon L. Veilleux
[EMAIL PROTECTED]
(860) 636-2683
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