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because the improvements largely resulted from significant reductions in pathlength and CPU,
environments that are constrained by other resources such as IO or memory may not show the same level
of improvements seen here.
Tuning changes in V6R1
As indicated above, most improvements will require no changes to an application. However, there are a
few changes that will require some tuning in order to be realized:
Using direct map (native JDBC)
For System i, the JDBC interfaces run more efficiently if direct mapping of data is used, where the
data being retrieved is in a form that closely matches how the data is stored in the database files. In
V6R1, significant enhancements were made in JDBC to allow direct map to be used in more cases.
For the toolbox and JCC JDBC drivers, where direct map is the default, there is no change needed to
realize these gains. However, for native JDBC, you will need to use the "directMap=true" custom
property for the datasource in order to maximize the gain from these changes. For Trade 6.1,
measurements show that adding this property results in about a 3-5% improvement in throughput.
Note that there is no detrimental effect from using this property, since the JDBC interfaces will only
use direct map if it is functionally viable to do
Use of unix sockets (toolbox JDBC)
For toolbox JDBC, the default is to use TCP/IP inet sockets for requests between the application
server and the database connections. In V6R1, an enhancement was added to allow the use of unix
sockets in a 2-tier toolbox environment (application and database reside on the same partition). Using
unix sockets for the Trade 6.1 2-tier workload in V6R1 resulted in about an 8-10% improvement in
throughput. However, as the default is still to use inet sockets, you will need to ensure that the class
path specified in the JDBC provider is set to use the jt400native.jar file (not the jt400.jar file) in order
to use unix sockets. Note that the improvement is applicable only to 2-tier toolbox environments. Inet
sockets will continue to be used for all other multiple tier toolbox environments no matter which .jar
file is used.
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Using 'threadUsed=false" custom property (toolbox JDBC)
In toolbox JDBC, the default method of operation is to use multiple application server threads for
each request to a database connection, with one thread used for sending data to the connection and
another thread being used to receive data from the connection. In V6R1, changes were made to allow
both the send and receive activity to be done within a single application server thread for each
request, thus reducing the overhead associated with the multiple threads. To gain the potential
improvement from this change, you will need to specify the "threadUsed=false" custom property in
the toolbox datasource, since the default is still to use multiple threads. For the Trade 6.1 workload,
use of the this property resulted in about a 10% improvement in throughput.
Tuning for WebSphere is important to achieve optimal performance. Please refer to the WebSphere
Application Server for iSeries Performance Considerations or the WebSphere Info Center documents for
more information. These documents describe the performance differences between the different
WebSphere Application Server versions on the System i platform. They also contain many performance
recommendations for environments using servlets, Java Server Pages (JSPs), and Enterprise Java Beans.
IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
©
Copyright IBM Corp. 2008
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