DB2 10 for Linux on System z Using z/VM v6.2, Single System Image Clusters and Live Guest Relocation

Chapter 4. DB2 Self-tuning memory manager and z/VM live guest relocation 33

The z/VM page allocation can be seen in Example 4-17.

Example 4-17 z/VM Page allocation snapshot.

q alloc page

EXTENT EXTENT TOTAL PAGES HIGH %

VOLID RDEV START END PAGES IN USE PAGE USED

------ ---- ---------- ---------- ------ ------ ------ ----

SSI4P2 9E2D 1 10016 1761K 708049 1454K 39%

------ ------ ----

SUMMARY 1761K 708049 39%

USABLE 1761K 708049 39%

Ready; T=0.01/0.01 15:04:07

Example 4-18 shows the z/VM storage allocation report from the IBM VM Performance

Toolkit.

Example 4-18 Performance Toolkit z/VM storage allocation report

FCX103 CPU 2817 SER B3BD5 Interval 15:02:29 - 15:03:29 Remote Data

Main storage utilization: XSTORE utilization:

Total real storage 8'192MB Total available 2'048MB

Total available 8'192MB Att. to virt. machines 0kB

Offline storage frames 0 Size of CP partition 2'048MB

SYSGEN storage size 8'192MB CP XSTORE utilization 100%

Shared storage 7'320kB Low threshold for migr. 4'480kB

FREE stor. subpools 3'756kB XSTORE allocation rate 32/s

Subpool stor. utilization 87% Average age of XSTORE blks 13057s

Total DPA size 8'069MB Average age at migration 71546s

Locked pages 3300

Trace table 1'300kB MDCACHE utilization:

Pageable 8'054MB Min. size in XSTORE 0kB

Storage utilization 114% Max. size in XSTORE 2'048MB

Tasks waiting for a frame 1 Ideal size in XSTORE 97'452kB

Tasks waiting for a page 0/s Act. size in XSTORE 577'536 B

Standby real stor. size 0kB Bias for XSTORE 1.00

Reservd real stor. size 0kB Min. size in main stor. 0kB

Max. size in main stor. 8'192MB

Paging / spooling activity: Ideal size in main stor. 0kB

FCXVMC111I Critical exception message(s) issued

From the Performance Toolkit report shown in Example 4-18, the storage utilization has

peaked to about 114%, which means that the LPAR is already overcommited on memory. We

did not want to resolve the critical exception reported here since the purpose of the test was

to find how STMM adjusts the resources during a relocation.

4.3.8 Load generation and database memory setup

We followed the same procedure for setting up the database memory configuration and then

simulating the workload as in the previous sections. The only exception was that the current

Note: As a general rule, paging space on DASD should not be allowed to eclipse 30%

utilization because the available paging space can become very fragmented and can

degrade the performance of the overall environment.