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

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V7 CLI
V7 and V8 Real Storage Comparison
V8 CLI
V7 JDBC
V8 JDBC
V7 EMB
Figure 4-6 Real storage comparison DB2 V7 vs. V8
V8 EMB
V7 SQLJ
V8 SQLJ
Other
DIST
DBM1
The “OTHER” bar in the graph represents the sum of the real storage consumed by MSTR,
IRLM and other system address spaces. As you can see, this is fairly stable for all the tests.
We see an increase in both the DBM1 address space and the DIST address space real
storage usage, as we execute the same workload levels (500 DBAT threads) for each
distributed workload.
There is a real storage increase of 20% in the JDBC application within the LPAR. For JDBC,
the DBM1 real storage increases 29%, the DIST real storage increases 169%. Overall, the
DIST address space uses far less storage than the DBM1 address space, even in V8. So, the
huge increase in DIST address space storage should not be considered a big problem,
unless you have a large distributed workload and are already real memory-constrained.
Although this is not shown on the graph, the MSTR address space also sees an increase of
19% over V7. However, as the MSTR address space only has a small storage footprint, we do
not consider this a problem.
Similarly, the IRLM real storage increased 139%. This is also not shown on the graph. For the
test workloads we used, the IRLM is not a huge consumer of storage, even in V8, since the
workloads we use do not generate a large amount of locks. Your workloads probably generate
many more locks and drive IRLM real storage requirements a little more, since many
customers generally run a large and very diverse mix of workloads concurrently, which in turn
tends to generate more locking activity. The IRLM requires more real storage in V8, primarily
due to the increase in size of IRLM control blocks. We therefore recommend you also
consider the IRLM storage requirements in your real storage estimates.
Real storage values for MSTR and IRLM do not change much and are included under
OTHER.
Chapter 4. DB2 subsystem performance 155