Q and A

Asked and Answered

I've been wrestling with a performance problem for several weeks (high class 3 wait times in an accounting report). The problem originally surfaced during a stress test with a Websphere/Java/DB2 Connect/DB2 for z/OS application, but the same high wait times have now been observed running one of the problem queries with a stress test using batch SPUFI (to eliminate the Websphere/Java/DB2 Connect components). Any way for me to determine how much virtual storage my DBM1 address space is currently using?

Robert Catterall responds:

As for sizing the virtual storage utilization of your DBM1 address space, you might check out a column I wrote a few months ago for DB2 Magazine called "Virtual Realities." It includes some information on the DBM1 storage uses that you have to account for in sizing address space capacity utilization. (You can find the online version of the article here: http://www.db2mag.com/ db_area/archives/2002/ q4/db2dba.shtml)

Keep in mind that if your mainframe server has 64-bit hardware addressing capability and your DB2 for OS/390 release level is at least Version 6, you can advantageously move your DB2 virtual buffer pools from the DBM1 address space to one or more OS/390 data spaces, freeing up a lot of DBM1 space (and offering major expansion capability for your buffer pool configuration — you'd do away with hiperpools and just go with lots of DB2 buffer pool space in data spaces.

See a complete archive of reader/author Q&As