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

Table 8-1 shows extracts from DB2 PE statistics reports for an Online Transaction Processing
workload (OLTP). The two columns of numbers within each z/OS represent values per
transaction for data sharing member 1 and member 2.
Table 8-1 CF Request Batching - DB2 PE extract (OLTP)
It can be clearly seen from Table 8-1 that CF request batching was not used in z/OS 1.3. The
counters for “Write & Register Multi”, “Pages Write & Reg Multi” and “Read for Castout Multi”
are all zero in z/OS 1.3.
CF request batching was used under z/OS 1.4:
► An average 0f 6.9 pages were written per WARM command
“Pages Write & Reg Multi” / “Write & Register Multi”=4.09 / 0.59
= 6.9
► An average of 7.7 pages were read per RFCOM command.
(“Pages Castout” - “Read for Castout”) / Read for Castout Multi”
= (4.61 - 0.01) / 0.60
= 7.7
Table 8-2 shows extracts from RMF reports for the same OLTP workload.
Table 8-2 CF Request Batching - RMF extract (OLTP)
As we can see from Table 8-2, the test using z/OS 1.4 results in significantly fewer requests to
the coupling facility (9,880 compared to 14,082 for this workload). This is the direct result of
CF request batching. We can also see the service times for both synchronous requests and
asynchronous requests to the coupling facility have increased slightly. On average, the
coupling facility is doing more work per each request, as a number of page movements may
need to be processed with each request. We also notice the coupling facility utilization has
322 DB2 UDB for z/OS Version 8 Performance Topics
z/OS 1.3 z/OS 1.4
Member 1 Member 2 Member 1 Member 2
Pages Castout 3.91 4.35 3.71 4.61
Write & Register 6.28 6.29 2.22 2.22
Write & Register Multi 0.00 0.00 0.59 0.59
Pages Write & Reg Multi 0.00 0.00 4.09 4.09
Read for Castout 3.91 4.35 0.00 0.01
Read for Castout Multi 0.00 0.00 0.48 0.60
z/OS 1.3 z/OS 1.4
Requests / sec 14,082 9,880
Sync requests
Serv time
(usec)
Async requests
Serv time
(usec)
% of all req 17.7 95.5 19.5 86.6
% of all req 173.9 4.4 192.8 13.3
CF utilization (%) 21.7 21.0