SAP Portal 7.0 with Microsoft Cluster Installation
I have installed Portal 7.0 on windows 2003 with MSCS in quality assurance system. As per installation guide I put an Dialog instance on Node 2. I am not clear about this as, from node 2 I can't run visual administrator or any configuration since all software files are not installed on Node as with CI installation. I have two questions here?
1. Is dialog instance installation is good enough for clustering.
2. Can I install Central Instance on Node 2 as well?
Please provide some feedback or re-direct to another thread. Thanks in Advance.
Vyacheslav Plyushchikov replied
1. Below is a description of the standard MSCS install supported by SAP.
On MSCS you have installed central instance (CI) locally one Node 1, Dialog instance (DI) on Node 2 and SAP Central Services (SCS) on clustered group.
This is normal.
Your Visual Admin and Config Tool will work only on Node 1, where you have CI.
MSCS installation does not provide redundancy of your admin tools.
It is designed to provide High Availability via failover of Single Point Of Faluire (SPOF): DB and services of SCS: message server and enqueue server.
In other words it will make sure system will be available and operational for users in case one node is down.
This will give you an ability to restore your node from the backup.
See SAP Note 112266 "19. Loss of a node"
2. It is not possible to have 2 CIs in the system.
3. Interestingly enough, after 1 and 2 have been said, it is possible to have CI clustered and available for failover, like SCS, in certain cases.
See SAP Note 112266:
"14. Does SAP support additional application servers (central or dialog instance) in a cluster?"
A purely clustered central instance (without a database) can be supported, if SAP is of the opinion that such a configuration makes sense and there is no alternative.
Reason: Each SAP instance requires a SAPLOC and, in part, a SAPMNT share. However, Windows shares cannot be virtualized. In other words, there can only be one SAPLOC or SAPMNT share per cluster. To get by with only one SAPLOC share, all SAP systems would have to run in one cluster group. However, this runs contrary to the principle of high availability.
Hope this helps,