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

time for an insert increases by 3.7% and the CPU time by 17% due to the architectural
changes in DB2 V8.
If we change the requesting application to insert an array of 10, 100, 1000 or 10000 rows
each with 20 columns we notice that the corresponding elapsed time at the DRDA application
requestor and CPU time at the DRDA application server drop significantly compared to the 1
row insert in DB2 V7. The best result is obtained with a rowset size of 10000 where the DRDA
application server CPU time is reduced by -72% and the DRDA application requestor elapsed
time by 89%.
(seconds)
9
6
3
0
Multi-row Insert, Distributed - Host to Host
(Total rows Inserted : 100,000 rows)
Requester Class 1 Elapsed time Server Class 1 CPU time
7.9
8.2
v7 v8 10k 1k 100 10 (n1)
default 10 100 1K 10K (n2)
V8 default = V8 without explicit multi-row Insert
V8 n1 x n2 = V8 with explicit multi-row Insert,
n1= # of Insert SQL calls
n2= # of rows per MR Insert SQL call
Figure 7-3 Multi-row INSERT - Distributed host to host
1.8
1.3
1 0.9
v7 v8 10k 1k 100 10 (n1)
default 10 100 1K 10K (n2)
Conclusion
With implicit multi-row FETCH your applications will benefit immediately from the multi-row
FETCH enhancement in a host to host DRDA environment without having to change the
applications. Explicit multi-row support requires an application change. Host variable arrays
are used to receive multi-fetch rowsets or serve as input for multi-row INSERT.
Recommendation
In host to host DRDA multi-row operations the best performance is obtained when the size of
the host variable array matches the query block size which is 10 MB or 32767 rows whichever
limit is first reached. Program virtual storage usage increases with the size of the arrays used.
Explicit multi-row operations require DB2 V8 in new-function mode (NFM).
In general, 100 rows is just about the maximum needed to get the optimal performance.
There is very little return beyond 100.
(Sec)
2
1
0
1.6
1.88
0.73 0.68
0.49 0.45
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