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August 28, 2012

Monitoring Buffer Pool Use of 1MB Page

Last week I discussed John Campbell's great presentation on migrating to DB2 10 and, more specifically, the need to add real memory to your system to help reduce CPU usage.

After reviewing John's presentation, I wondered how you can determine when a buffer pool is taking advantage of 1MB page size.

In an atttempt to answer this question, I searched the DB2 10 Administration Guide, the DB2 10 Command Reference Guide and the DB2 10 Managing Performance manuals. Then I searched IBM's DB2 10 for z/OS Information Center. Nothing.

Finally, I went back to IBM developerWorks, the source of the Campbell presentation. Bingo. This page lists some storage fixes, but it also references the Display Bufferpool command with this new parameter that I have never seen: SERVICE=4.

I issued the display command with the service =4 parameter on my system and received this output:

 

-DISPLAY BUFFERPOOL(BP1) SERVICE=4;    ** Where BP1 is the buffer pool name you are interested in.

DSNB401I  !D10A BUFFERPOOL NAME BP1, BUFFERPOOL ID 1, USE COUNT 10

 DSNB402I  !D10A BUFFER POOL SIZE = 10000 BUFFERS  AUTOSIZE = NO

              ALLOCATED       =     9594   TO BE DELETED   =        0

              IN-USE/UPDATED  =      480

 DSNB406I  !D10A PGFIX ATTRIBUTE -

              CURRENT = NO

              PENDING = NO

            PAGE STEALING METHOD = LRU

 DSNB404I  !D10A THRESHOLDS -

             VP SEQUENTIAL    = 80

             DEFERRED WRITE   = 30   VERTICAL DEFERRED WRT  =  5,  0

             PARALLEL SEQUENTIAL =50   ASSISTING PARALLEL SEQT=  0

 DSNB999I  !D10A DSNB1DBP  SERVICE( 4 )OUTPUT

 DSNB999I  !D10A 4K PAGES 9594

 DSNB999I  !D10A 1M PAGES 0

 DSN9022I  !D10A DSNB1CMD '-DIS BUFFERPOOL' NORMAL COMPLETION

 

Notice message DSNB406I shows PGFIX (page fix) set to "No," and Message DSNB999I says no 1MB pages are allocated. This makes sense because of the page fix setting. As I noted last week, page fix must be set to "Yes" to take advantage of the 1MB page size.