Intel AS/400 RISC Server, 170 Servers manual Tuning changes in V6R1, Using direct map native Jdbc

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:

yUsing 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 so.

yUse 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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yUsing ‘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	Chapter 6 - Web Server and WebSphere	94