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

For the same buffer pool size and other configuration settings, in general, a 1 to 20% increase
in demand for real storage for medium to large DB2 V8 subsystems is experienced. For
smaller DB2 subsystems, we experience a higher increase. Measurements have seen as little
as 4 to 5% increase demand for real storage, in the workloads used.
Your mileage will definitely vary, depending on the type of DB2 workload (for example, simple
OLTP SQL compared to complex, query-based SQL) and the current demands DB2 is placing
on your real storage. It is important to ask if DB2 is a major user of real storage on your
system or a minor user of real storage.
We first compare real storage measurements for various distributed workloads. These
scenarios tend to be a “worst case” for studying real storage requirements in DB2 V8,
because the DIST address space storage has also increased in V8, which also drives the
demand for real storage in the LPAR. Normally you would see less demand on real storage
when you are only running a local workload since the DIST address space is not used.
Distributed performance
We can make the following conclusions about the performance data in Table 4-8.
The real storage used for CLI ODBC and embedded SQL workloads is significantly less than
those for JDBC and SQLJ. The real storage increase on an LPAR basis is as high as 20% for
the JDBC workload, compared with 11% for the CLI workload.
Table 4-8 Real storage comparison for CLI, JDBC, embedded SQL, and SQLJ workloads
Real storage in
MB for LPAR
Figure 4-6 illustrates the difference in real storage between DB2 V7 and V8 for the same
series of performance tests already discussed in this section. We measure the real storage
consumed for the different workloads comparing DB2 V7 usage to that of V8 for the DBM1
and DIST address spaces. As you can see, the real storage growth in DB2 V8 is significant
and something you need to prepare for, as you migrate to V8.
154 DB2 UDB for z/OS Version 8 Performance Topics
CLI JDBC Embedded SQL SQLJ
V8 V7 to V8%
increase
V8 V7 to V8%
increase
V8 V7 to V8%
increase
V8 V7 to V8%
increase
1196 11% 1410 20% 1175 11% 1238 18%
DBM1 547 24% 688 29% 566 29% 523 25%
DIST 70 64% 137 169% 74 73% 63 45%
IRLM 5 139% 5 139%
MSTR 19 19% 18 19%
OTHER 555 -3% 563 -2% 535 -8% 652 12%
Note: The row name OTHER records the real storage consumed by the whole LPAR minus
those address spaces separately listed in the table.
The real storage values for IRLM and MSTR were not separately captured for the static
cases; as a result, these times are reflected in the table under OTHER. The real storage
consumed by the IRLM and MSTR address spaces does not have significant changes from
the values already noted for the CLI and JDBC tests.