Concept of SAP Clustering in Windows

Question

Dear Experts
I  am Installing the SAP ECC6 EHP4 Clustering in the Windows 2003 Enterprise Edition.  I have completed the windows Clustering MSCS and Database Clustering SQLSERVER 2005  in the NODE A and NODE B.  I also aware that i need to install the Replication Server in NODE A and NODE B. My Doubt is whether ASCS in NODE B is Mandatory? and  Dialog Instance is also Mandatory ?

Answer 1

Hi,
Following are the instances we need to install in HA system installation
1) DB instance
2) ASCS & SCS instance
3) CI / Dialogue Instance
Designing of cluster environment is depends on your infrastructures. As you mentioned its two node cluster you can go as follows.
DB instance and ASCS & SCS instances are the single point of failure. So these instances needs to be registered/installed in both the node A & B, so that instances can run on both the node in case of failure of one node.
Now, you can run all these instances in single node or if you want to sare the h/w load you can put DB instance in Node A(primary) and ASCS & SCS in Node B (primary).
In such case if Node A fails DB instance move to Node B and if Node B fails ASCS and SCS instance move to Node A.
Now if you have additional h/w for dialogue instance then install it seperately. If you don't have additional h/w then you can install as following option
1. One DI in Node A & one in Node B.
2. One DI in any Node & register as cluster component. So if primary node of DI fails it moves to other node .
Note : I explain a scenario only which may be feasible. Please follow the installation guide where you get all in details