Introduction
SAP Note 1495160 - SAP JVM as replacement for Partner JDKs 1.4.2 announcing the replacement for Partner JDKs 1.4.2 by SAP JVM 4. Just recently SAP officially released SAPJVM 4 for Windows, Solaris and Linux (not all types). The other platforms such as HP/UX, IBM i, AIX and more Linux types will follow in mid 2011.
The end of support for Partner JDK is set to October 1st 2012 for now. Date/time is still subject to change. This will affect all SAP Netweaver 6.40 and SAP Netweaver 7.0x AS Java based SAP systems.
Technical integration
SAPJVM 4 is not integrated in the same way as SAPJVM 5 or SAPJVM 6 or higher. From a technical point of view SAPJVM 5 is a separate Java component and can be updated automatically through JSPM. SAPJVM 5 and higher uses an ICM as dispatcher which is also a major technical difference.
A switch to SAPJVM 4 can take place automatically through the Switch Tool provided by SAP but operations like an update are to be done manually as SAPJVM 4 is not integrated as a separate Java component you cannot use JSPM to automatically update it. Since SAPJVM 4 doesn’t really touch the architecture, you will also have a dispatcher node as you would have when you run on Partner JDK.
This also means that when you look up SAP notes with a generic header like SAP Note 1133020 - How to import a SAP JVM patch into an AS Java you have to check the Affected Releases mentioned in the SAP note because this note and some other notes are not applicable to SAPJVM 4.
Switch tool
The preferred way to switch to SAPJVM 4 is using the switch tool provided by SAP. You can find information on the download location for the switch tool in SAP Note 1555341 - Downloading SAP JVM Switch Tool and SAPJVM 4. The switch tool uses SAPinst which is also used for SAP system installations so administrators should be familiar with how it works.
The switch tool runs you through a number of screens just like a traditional SAP installation would. Among those screens are screens which propose new parameter settings for the virtual machine as they can be very different depending on which partner JDK your virtual machine was running.
SAP Note 1522200 - SAP JVM 4.1 parameters when switching from a partner JDK provides an overview of the currently recommended parameters so I would recommend you check if the note is updated when you decide to switch to make sure the latest parameter recommendations are met.
Roll back changes in case of issues
If you bump into serious issues and you cannot get them resolved within an appropriate time frame there is the possibility to roll back the changes using instructions (script) which is written by SAPinst into the SAPinst installation directory. The file switchJDK.txt contains the instructions to roll back the changes.
Performance tests
The question should you do performance tests? I would say “yes”, of course it depends on how critical your applications are which are running on SAP Netweaver 6.40 / 7.0x AS Java based systems. If you have a SAP Netweaver Portal 7.0x for example which is used for ESS/MSS purposes I would recommend you go for performance tests / stress tests and compare the results from before and after the switch.
It stays a fact that the performance is not always better by default. Even if the performance is good you might want to try out a few different fine tuning parameters to further enhance performance based on the usage type of the system and the activities performed on it.
SAPJVM is based on the binaries provided by the Oracle (Sun) so you can check out whitepapers and documentation from Oracle to help you further tune your virtual machine. A rather compact whitepaper that is worth taking a look at is the Java Tuning White Paper.
Wily Introscope
The preferred monitoring tool for AS Java based SAP systems is still Wily Introscope. Most customers have Wily Introscope in place as part of the E2E Root Cause Analysis scenario on SAP Solution Manager (also referred to as diagnostics). In order to have proper interpretation of concurrent mark sweep garbage collection make sure your LM-Service support package stack level is up to date. It doesn’t necessarily mean you have to perform a support package stack upgrade (unless you are way behind on SPS level) but you at least should implement the latest bug fix patch available.
One thing that might be confusing is the fact that the introscope agent probe directive sap_sapjvm.sar should not be enabled for SAPJVM 4 as it was build for SAPJVM 5.1 – SAP Netweaver 7.1 and is not compatible for SAPJVM 4.
Don’t forget that since you have a dispatcher it is recommended to integrate it into Wily Introscope as well. The procedure is described in the attachment of SAP Note 1424719 - Wily Introscope Instrumentation for SAP J2EE Dispatcher.
