SAP Java stack architectural differences from ABAP stack?

My company is thinking to upgrade SAP from 46C to ECC 6.0 EHP开发者_如何学C 5 and we have the next 3 questions:

1) What is the difference between ABAP Stack and Java Stack. I imagine 46C is "ABAP stack"?

2) In which cases it is absolutely necessary to install the Java Stack?

3) Does the installation of the EHPs imply that we should first install the Java Stack?

Thanks

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SAP ECC (all core modules) runs on the ABAP stack. Many of SAP's interoparability modules like SAP PI runs on the Java Stack. If you intend to use SAP PI you will most likely need to install the Java Stack, but you should be able to upgrade to ECC6 without having to install the Java stack.

You do not require the Java Stack to apply Enhancement Packs.

A few years back there was a push to move more toward the Java stack, but I believe SAP has gone back on that position. Nowadays you can use Web-Dynpro for ABAP for web-development in SAP as well as Web-Dynpro for Java.

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Just for the record:

• Up until release 4.6C there were only ABAP instances.

• After that (mainly releases 6.x and 7.0x) it was possible to install Java-only instances or combined ABAP+Java instances. The latter are so called double-stack systems. The stacks share some internal ressources (kernel files, database, etc) but are pretty independent on the front side. Somehow like Siamese twins joined at the hip.

• Due to stability the double-stack systems are not supported any more. This from release Netweaver 7.3 onwards (but there are certain exceptions). There is even a procedure to split a double-stack into two independent systems.

So if a double-stack system is upgraded via Enhancement Package it must be applied to both stacks.

Otherwise install separate ABAP and Java systems as needed and set up the required connections: RFC, JCo, SOAP, etc.

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1) What is the difference between ABAP Stack and Java Stack.

The one is an application server that runs ABAP programs, the other is an application server that runs Java programs.

I imagine 46C is "ABAP stack"?

4.6C only provides an ABAP stack.

2) In which cases it is absolutely necessary to install the Java Stack?

Whenever you need something (like the Adobe Interactive Forms or some Portal stuff) that requires the Java Stack.

3) Does the installation of the EHPs imply that we should first install the Java Stack?

No. In fact, adding a secondary step should be an entirely different project from upgrading an existing system - you should not combine these to keep complexity at bay...