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

Trans/second - higher is better
250
200
150
100
50
0
9 %
KeepDynamic YES
20 %
ITR AIX ITR z/OS
keepdyn no
keepdyn yes
Figure 7-18 DB2 Universal Driver - KEEPDYNAMIC YES
SpecJApp2002
WebSphere/AIX V502- DB2 for z/OS V8
ITR = tps/cpu%*100
CPU is saved on the client (WebSphere) and in DB2 on the server. Throughput improved with
9% on the client and 20% on the DB2 server.
In order to benefit from performance improvements the following PTFs/APARs should be
applied: PQ86787/UQ87049, PQ87126/UQ88971 and PQ87129/UQ87633.
Conclusion
The statements are saved on thread level and can consume a significant amount of storage.
Type 2 distributed threads cannot turn inactive and DB2 resources for distributed threads are
not freed at commit. Therefore this is not recommended for storage constrained systems.
Recommendation
KEEPDYNAMIC(YES) is recommended for applications with a limited amount of SQL
statements that are executed very often. It is not recommended for applications with a large
number of SQL statements that are executed infrequently.
LOB streaming
In prior releases, Universal Clients and Linux, UNIX, and Windows servers had to read the
entire LOB to determine its length prior to flowing it to DB2.
LOB streaming, activated by the fullyMaterializeLobData property, allows the DB2 universal
client or a DB2 for Multiplatforms server to not know the total length of a LOB value prior to
sending a LOB value. This improves performance by eliminating the need to read the entire
LOB to determine its length prior to sending the LOB value. DB2 continues to provide the total
length of a LOB value, but it is now able to read in the LOB immediately without knowing the
exact length up-front.
The main benefit is performance. But there is another advantage. It is not always possible to
determine a LOB's attributes (like length and nullness) up-front, for example when a client is
acting on behalf of a CLI application that is being supplied with chunks of a LOB value in a
piecemeal fashion using the SQLPutData API. Therefore this improvement provides a more
flexible mechanism whereby the sender can defer indicating the nullness and/or the length of
a LOB value until a chunk is ready to be sent.
Chapter 7. Networking and e-business 305