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

3.10.2 Conclusion
100 Inserts activated trigger 100 times
but WHEN condition evaluated to true only once
0
CPU non-nested CPU trigger
.
Figure 3-42 CPU time to invoke trigger but WHEN condition true once
The measurements of execution of triggers show:
► Saved work file usage
► CPU saving for avoided work file allocation if the rows fit into the work space
► Performance improvement depends on:
– Complexity of triggering SQL
– Complexity of SQL executed in the trigger
– Number of times the triggers are invoked
3.10.3 Recommendation
You don’t need to do anything, not even REBIND, to have the performance benefit if you are
using triggers that allocate work files.
3.11 REXX support improvements
CPU time - lower is better
0.02
0.015
0.01
0.005
The performance of REXX programs accessing DB2 tables is improved in V8 in the case of
programs issuing large numbers of SQL statements.
The improvement is due to two changes:
► DB2 V8 avoids loading and chaining control blocks for each REXX API invocation; they are
now built only at initialization time and then pointed to for the successive API calls. This
has reduced the CPU time.
► The REXX exec points to the DSNREXX code. The change now loads the modules and
keeps them in local application address space for the duration of the job whenever they
have not been preloaded in LPA. This avoids accessing the modules again from disk. This
90 DB2 UDB for z/OS Version 8 Performance Topics
-8.3%
-24%
DB2 V7
DB2 V8