SAP SCS Active/Active Clustering

[Former Member]

Hi Experts,

Our company is looking to setup a complete Active/Active clustering architecture for the SAP environment.

Our SAP Database will be Oracle RAC 11gR2.

We are also planning to have the Enqueue Server and Messaging Server (ASCS) on active/active configuration.

I have read from the SAP notes and other documents that SAP SCS is implemented as only Active/Passive and not as Active/Active.

Is this true?

Or can we setup an Active/Active cluster configuration for the SAP SCS as well?

Please let me know.

Another question is that I have learnt that using Web Dispatcher we could achieve an Active/Active configuration for load balancing but only for the web connections or sessions and not for the classic SAP connections. Can somone please clarify this?

The SAP Web dispatcher is only useful in the Web environment. In the classic SAP system, load is balanced by the message server.

What is the meaning of this?

So by making the message server active/active will I be able to achieve load balancing for the SAP SCS?

Please give me a clarification on this.

Thanks,

Augustine

[Former Member · Accepted solution]

>> So by making the message server active/active will I be able to achieve load balancing for the SAP SCS?

The message server can only be hosted on one host which named as central instance. It is not able to host on both nodes, at the same time.

As I noted in the my previous message, by the standard installation, dialog instances installed on on both hosts separately. As a result of it, the systems will be available by the active/active scenario.

And the load balancing between application servers will be available by using SAP web dispatcher.

Best regards,

Orkun Gedik

[Former Member · Accepted solution]

Thanks Orkun,

You are right. I understand that it is worth setting up an Active/Active Database configuration but not the case with an Active/Active configuration for the SCS or ASCS as the case may be as they are very light components and moving them/restoring the services to the next alternate node or server would be very quick and less resource intensive. So there is no point in having an active/active setup for the SCS and that is the very reason why SAP has not gone in for an Active/Active setup for the SCS. However the concept of have an active/active scenario due to Dialog Instances will have to be experienced by me and the team after we setup our system as we are yet to understand that part.

So thank you very much for your answers.

Best Regards,

Augustine Amalesh

[Former Member · Accepted solution]

Hi Augustine,

You'r welcome. Please feel free to ask, if you have any further questions.

Best regards,

Orkun Gedik

[Former Member · Accepted solution]

Hi Orkun,

I have posted another question today (Active/Passive For Oracle Database😞

http://scn.sap.com/thread/3288606

Please see if you are able to provide any inputs for that.

It is crucial for us as of now.

Thanks,

Augustine

[Former Member]

Hi Augustine,

>> I have read from the SAP notes and other documents that SAP SCS is implemented as only Active/Passive and not as Active/Active.

SCS can only be implemented as Active/Passive configuration. For the instance, while enqueue services installed and run on the NodeA, the other node replicates the enqueue entries. In short enqueue service can run only on one instance. When NodeA failed, enqueue service role transferred to the NodeB and continue the business process. This operation is regardless from the database HA point of view.

On the other hand, by the standard installation both hosts has a dialog instance, you can use them as active/active scenario.

In summary, SCS cannot be installed active/active, but because of both hosts has a dialog instance, you can use both systems as active/active scenario.

This scenario show some differences by different HA solutions.

>> The SAP Web dispatcher is only useful in the Web environment. In the classic SAP system, load is balanced by the message server.

Yes, it is correct.

Best regards,

Orkun Gedik