This edition of the SAP on IBM DB2 for i - News from Development blog intends to give you a short heads up regarding some new options for Java on IBM i with SAP Netweaver 2004 and 7.0. These options were triggered and facilitated with introduction of the IBM Technology for Java (IT4J) JDK 1.4.2 64-bit.
IT4J 1.4.2 64-bit is available from IBM since October 2008 with IBM i 6.1 and it is supported by SAP for all products based on SAP Netweaver 2004 and SAP Netweaver 7.0 starting from 12/01/2008. All subsequent product deliverables of SAP on IBM i 6.1 based on SAP Netweaver 2004 and SAP Netweaver 7.0 will utilize IT4J 1.4.2 64-bit as their default Java technology.
Based on our positive experience described below we also recommend to switch systems that were installed with already delivered software packages from Classic VM to IT4J.
Jumping on this JVM means aligning to IBM's overall Java strategy, and taking advantage of any further development. Note that IBM will not even provide Classic VM in any OS release higher than IBM i 6.1.
Installation
The new JVM can simply be installed as option 13 of license program 5761JV1 on IBM i 6.1. The few details to be known can be found in the most recent Information APAR II14362.
Once it is installed you can make interactive use of IT4J by setting environment variable JAVA_HOME to /QOpenSys/QIBM/ProdData/JavaVM/jdk14/64bit. Running the CONFIGJVM tool (see below) for the conversion of your SAP system initializes your administration users' environment automatically for use of IT4J.
Performance
According to IBM and to our own lab exerience IT4J gives two major improvements for you. First, it shows a significantly lower resource consumption in terms of memory footprint and CPU utilization. On the other hand we observe an obvious performance benefit. Therefore, using IT4J should enable you to save resources and cut down expenses regarding hardware.
This is also experienced and confirmed by our first customers having started to utilize IT4J during the pilot phase.
Our pilot customers reported that 'To run our SAP Java workload we are now using IBMs new IT4J JVM, which is even more efficient than IBM's previous IBM i Classic JVM. The IT4J JVM runs faster, while needing less CPU and memory resources.'
The following figures are taken from an Enterprise Portal workload. They are given to confirm the above statements, knowing that it is hard to extrapolate from lab measurements to your particular workload. You see a comparison of CPU utilization, first.
Below an average view of response times for certain activities is shown.
New support tool CONFIGJVM
One might be concerned by the need of reconfiguring a J2EE engine for use of a new VM with all its new and specific parameters. Therefore, SAP developed a tool that is supposed to do this sophisticated job for you. Being installed with patches for SAPJ2EE (#35 in 6.40, #41 in 7.00) and MENUS (#2 in each release) or with coming stack kernels, CONFIGJVM is fully integrated into the SAP kernel and can be reached and utilized via menu options:
You start from menu R3MAIN and choose options
7. "Define or Change SAP", followed by
4. "SAP Java Stack"
to end up with menu CONFIGJVM:
The switch is a simple as that:
- Run a preview and check in the logs if you like the changes.
- Stop your system.
- Run the switch (apply).
- Restart your system.
Jürgen Kohrell, Solution Architect from the consulting partner basycs GmbH regarding the switch procedure: "Moving from the IBM 'Classic' Java engine to the new IT4J engine was really quick. The conversion was easy to handle and only took less than an 1 hour."
In addition to support the switch from Classic VM to IT4J this tool is capable of and should be used for checking parametrization of your system with either JVM and for applying default settings with a certain range of variability.
Memory Analyzer Tool
When being published for the first time the Eclipse Memory Analyser Tool (MAT) gained pretty high attention in the Java community. This tool allows to analyze huge heaps as they evolve in an productive environment. MAT can understand system dumps that are written by IT4J 1.4.2 SR12 and later. This is a major step forward in terms of supportability of the Java stack on IBM i and other IBM platforms.
Note that running your system with IT4J is a mandatory prerequisite for using this tool.
Sources of information
IBM information:
- SAP NetWeaver Java on IBM i can serve as a starting point for gathering IBM information about IT4J.
- Although written for the 32-bit version of IT4J the IBM redbook IBM Technology for Java Virtual Machine in IBM i5/OS is very useful to understand the new JVM and to learn how to use it.
- The JVM Information section of IBM InfoAPAR for IBM i V6.1, II14362, contains up to date information about required patches and installation of IT4J
Note regarding IT4J and its configuration:
Notes describing CONFIGJVM and it's use:
- 1262494 IBM i: CONFIGJVM tool to check/modify JVM settings
- 1161275 IBM i: Switch WebAS Java from Classic VM to IT4J
MAT information:
https://wiki.sdn.sap.com/wiki/display/Java/Java+Memory+Analysis
http://www.eclipse.org/mat/
http://www.ibm.com/developerworks/java/jdk/tools/mat.html
Feedback
As this is new technology, and we want to continuously improve we encourage you to share your own experience with us by commenting on this Blog.
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