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

oltp
oltp in data sharing
batch insert
batch select
batch fetch/update
batch data sharing
batch drda
utility
query
Figure 4-1 CPU workload summary
CPU range by workload
-20% -10%
0% +10% +20%
The typical customer CPU regression of DB2 V8 is anticipated to be 0 to 10% more than V7
on average. This CPU degradation is the result of the new functionality that is provided in DB2
V8, together with the overhead that comes with 64-bit addressing.
Looking at it a little closer, the CPU delta is:
► 0 to +15% regression for online transaction workloads
Remember, we have much more code and function in V8 compared with V7, as well as
dealing with the added complication of 64-bit addressing in the DBM1 address space.
► -5 to +10% regression for online transaction workloads in data sharing environments
The reason why we are able to achieve less CPU degradation in data sharing is because
there are a number of performance enhancements in V8 that apply specifically to data
sharing environments. For example, Lock Protocol Level 2 to reduce global lock
contention. See Chapter 8, “Data sharing enhancements” on page 319 for more details.
► -5 to +20% regression in batch workloads
– -5 to +5% with a heavy INSERT workload
This does not represent a significant change and is comparable to DB2 V7.
– -5 to +20% with a heavy SELECT workload
We are able to achieve some CPU reduction for SELECT workloads because the
SELECT workloads benefit from the new lock avoidance techniques used in V8. See
4.13.4, “Lock avoidance enhancements” on page 214 for more details. Applications
using CURRENTDATA(YES) receive the most benefit as these do not exploit lock
avoidance in DB2 V7. We see more CPU degradation (up to a 20%) as the number of
columns increases.
– +5% to +20% with a heavy FETCH and UPDATE workload
This increase in CPU varies greatly based on the number of columns being processed.
The more columns, the more CPU used. In fact, you may see as much as 20% more
CPU consumed in V8 when you are processing over 100 columns in the SQL.
► -10% to +15% regression in batch workloads in a data sharing environment
Chapter 4. DB2 subsystem performance 131