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Add Java Stack - How to find-out additional HW requirements

jo_degraeve
Participant
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Hello

We are thinking of adding the Java stack to our current 640 ABAP ERP2004 system.

We won't add any Java functionality as yet, we just want to be prepared if the requirement for Java stack comes up.

How can I 'calculate' the required additonal HW (CPU/Mem) for the addition of the Java stack.

I suppose there is some overhead (even when the Java functionality is not yet used)

Or would I get this info by ordering an EarlyWatch Check and specify our intention to add the Java stack ?

Any good/bad experiences in the field with a Java stack on 640 ?

Jo

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Answers (3)

Answers (3)

markus_doehr2
Active Contributor
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Just to add::

Check

That page has some links to interesting facts when it makes sense to combine which applications (ABAP + Java) onto one system or where not.

Markus

Former Member
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Hi Jo,

We've been running a dual stack for BW for a couple of years now. It is more cumbersome to apply fixes to both sides which therefore extends your downtime window and on occasion the JSPM process needs a kick start to complete the apply.

Keeping the java server in a separate memory pool will help performance - we created one with 4gig and followed the tuning note (71736) to get the buffers right and 990892 for the properties - but things may have moved on a bit here - there's a redpaper Java on IBM i5/OS worth a read.

We also required to use adobe printing and dbconnectivity to external SQL data bases which meant we had to install an application server; this also meant that we had to stay with the toolbox JDBC driver rather than the native JDBC driver which is faster. This I think also means we will be limited to staying on this driver rather than moving to the much better performing IT4J JVM when we upgrade to V6R1 shortly - is this the case Christoph ?

Regards

David

Former Member
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Hi David,

no, JVM and JDBC are two different things. When you upgrade your i5/OS to 6.1 you should definitely go to IT4J and this is not limited by any JDBC driver. As for the JDBC driver, it is true that you are limited to the toolbox driver when you are using remote application servers. You can't use the native driver then.

As for settings: The entry point for the Classic JVM is SAP note 717376 and for IT4J it is SAP note 1234382. When you want to cleanup settings (e.g. as advised in note 990892) my recommendation is to use the new CONFIGJVM tool which is described in SAP note 1262494. This greenscreen tool checks (and fixes) the most important parameters on all known places. You avoid the hassle of having to find all places manually via configtool and in several configuration files. CONFIGJVM is also the tool to use when you want to switch from Classic JVM to IT4J.

Best regards,

Christoph

Former Member
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Hi Jo,

I agree to Markus' oppinion, I would not add a JAVA stack as ADDIN to the ABAP system, unless it is absolutely necessary. This spares effort and trouble when maintaining the system, e.g. SP installation or upgrade.

If you want to install a Java stack, "just to play around", my recommendation is to install a Java singlestack system. It is difficult to say what the requirements are. If you want nice performance, you should probably have 1 additional CPU and 6 additional GB of main memory. However, everything depends on the workload on the system. If the system is merely hanging around, maybe 1/2 CPU and 3 GB of main memory are enough.

Having a single stack Java system has also the benefit that you can stop it, in case resources are low on the system.

Hope that helps a bit,

Christoph

PS: You should use IBM i 6.1 and the IT4J JVM

markus_doehr2
Active Contributor
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I personally would not install a Java AddIn into an ABAP system, I would install a separate box. This makes upgrading easier (with a Java Addin you have to run two upgrades in parallel) and you can better size the system.

Markus