DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

The results indicate no significant difference in throughput for our workload running in CM
compared with NFM. We recorded less than 1% variation which is not significant.
We see 7% more class 2 accounting CPU consumed in V8 compared with V7 and slightly
less CPU used in NFM compared to CM, with a less than 2% improvement. We can therefore
conclude there is no significant difference in CPU consumed by using DB2 V8 in CM over
NFM.
We also see a modest increase of 2% CPU consumed by each transaction in DB2 V8 CM
compared with DB2 V7. This would have been a little higher if CPU consumed by the DBM1
address space had not decreased by 20% compared with V7. The DBM1 address space
used less CPU because all the buffer pools were long term page-fixed and all the plans and
packages were bound in the V8 format.
In addition, we see a 7% increase in class 2 CPU time used by each transaction in DB2 V8
CM compared with DB2 V7. This increase is caused in part by the extra CPU required to
process the 64-bit instructions necessary to access the DBM1 memory structures which are
now above the 2 GB bar.
Table 4-2 compares the IRWW workload running in DB2 V8 compatibility mode, with DB2 V8
new-function mode, in a data sharing environment.
Table 4-2 CM vs. NFM - Data sharing
DBM1 0.407 0.324 0.321 - 20% - 1%
IRLM n/c n/c n/c
Total 0.503 0.431 0.428 - 14% - < 1%
DB2 class 2 CPU
+ Total
134 DB2 UDB for z/OS Version 8 Performance Topics
DB2 V7 DB2 V8
CM
DB2 V8
NFM
Delta
(CM / V7)
Delta
(NFM / CM)
2.216 2.273 2.246 + 2% - < 2%
DB2 V7 DB2 V8 CM DB2 V8 NFM Delta
(CM / V7)
Page-fixed Buffer Pools No Yes Yes
Locking Protocol Level 1 1 2
ETR
(commits / sec)
287.83 287.50 285.33 283.67 290.00 289.83 - 1% + 2%
CPU (%) 67.32 72.60 65.33 70.22 62.29 61.95 - 3% - 8%
Group ITR
(commits / sec)
DB2 class 2 time
(msec / Commit)
Delta
(NFM / CM)
823.56 840.72 933.41 + 2% + 11%
Elapsed 34.272 34.859 36.713 39.179 19.415 19.442 + 9% - 49%
CPU 2.204 2.380 2.440 2.643 2.525 2.508 + 8% - 1%