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Win2K3 Cluster - DB and CI

Former Member
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Hello,

We want to cluster SAP ECC 6.0 for the Database Instance and Central Instance servers on Windows Server 2003 running SQL 2005.

On following the SAPinst guide, it is mentioned that only only ABAP Central Services Instance and Database Instance should be configured as failover in MSCS cluster. Central Instance and Dialog Instance should be installed on any single node on the local disk or outside the MSCS node.

I have doubt about this. If i install CI on any one cluster node locally, what would happen if this server fails ? I want to install the Central Instance as failover too.

Please guide.

Thanks in advance.

Kalpesh.

Accepted Solutions (1)

Accepted Solutions (1)

brian_walker
Active Participant
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Kalpesh,

The installation guide is correct. The "central instance" is a bit of a misnomer these days. It is nothing more than the first installed dialog server at this point. The central services will be installed in the cluster and the second "dialog instance" can run just fine when the "central instance" is down. The only thing that is on the central instance that is not on additional dialog instances are the J2EE tools like Visual Admin and Config Tool (in /usr/sap/<SID>/<INSTANCE>/j2ee. This is not a big deal.

You will want to change your instance profiles and make sure that all application servers have dialog, batch, spool, update, and update2 processes so that they can function on their own. You may also want to add a gateway to the ABAP central services instance so that you have an HA gateway.

Brian

Former Member
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Hello Brian,

Thanks for reply and guidance.

To be frank, i am new to SAP. The consultants who are installing it says, that CI is required for the users to login. They cannot login if CI is not available. Can you please clear this point ?

We have 2 node cluster. I will install CI and DI in the second node. If its true that users cannot login after CI goes down, then what is the point of having DI and ASCS being clustered ?

I think i am not yet clear how and where to install the CI and how would it function in a 2 node cluster. Can you guide me to my below doubts,

I install Database Instance and ASCS as clustered resources with global hosts configured.

I install Central Instance in the second node - locally

I install Dialog Instance in the second node - locally

If second node goes down, what would happen ?

Please guide

Thanks again

Kalpesh

brian_walker
Active Participant
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Kalpesh,

Your consultants do not know what they are talking about if they have said this. As I stated previously, as long you install the database and the ASCS/SCS in a cluster and at least one member of that cluster is up and providing those services, then you are fine. This is exactly what we do at my company and we perform maintenance on one of the instances while users are able to continue using the other instance.

The central instance is nothing more than another dialog server in this case. As long as you have taken care to do what I indicated previously and adjust the instance profile of each dialog instance so that there is at least one dialog, batch, spool, update, and update2 process then it is completely UNTRUE that users will not be able to login to SAP if at least one such dialog instance is running.

When you ask:

"I install Central Instance in the second node - locally

I install Dialog Instance in the second node - locally

If second node goes down, what would happen ?"

I hope you mistyped that. If you installed both the central instance (first dialog install) and an additional dialog instance on the same hardware and operating system instance, then if you take that down and thus neither of the SAP instances are available, then of course, no users will be able to login to SAP. If instead you meant that the dialog instance would be installed on a different hardware "node", then the users will be able to login to SAP on whichever instance is still available, whether it is the "central instance" or the additional dialog instance.

Please let me know if you need further clarification.

Brian

brian_walker
Active Participant
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To be even more clear...

What we do is to have 4 different "nodes". These are completely seperate hardware/OS systems.

2 of these nodes are for the database and ASCS/SCS and they are part of a MSCS. Usually one is the primary for the database and the other the primary for ASCS/SCS just to spread the workload around

1 of these nodes is for the "central instance"

1 of these nodes is for the "additional dialog instance"

While the "central instance" and "additional dialog instance" could be installed on the nodes running MSCS, we have chosen not to do this. If that is something you are exploring, you would need to install the "central instance" on one MSCS member and the "additional dialog instance" on the other so that you always have a database, ASCS/SCS, and a dialog server available in a failover situation. I would not recommend doing so for production.

Brian

Former Member
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Hello Brian,

Thanks for your receptive reply. It is now very clear.

I will cluster Database Instance and ASCS.

I will install CI on first node locally.

I will install DI on second node locally.

As you have mentioned installing CI and DI locally on the MSCS node is not recommended, we shall discuss about that.

About the steps you have mentioned as below

"You will want to change your instance profiles and make sure that all application servers have dialog, batch, spool, update, and update2 processes so that they can function on their own. You may also want to add a gateway to the ABAP central services instance so that you have an HA gateway."

Can you be more precise on this ? To make sure that all application servers have dialog, batch, spool, update, and update2 processes so that they can function on their own, means to run them as service ?

To add a gateway to ABAP CI instance is to have a virtual host/ip for it ?

Thanks again.

Kalpesh.

Former Member
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Hi Kalpesh,

I) installed j2sdk 17 in both the nodes.

2) installed DB2 in both the nodes local C drive.

3) Installed ASCS and SCS in virtual hostname in shared disk.

4)Database instance with virtual hostname in the shared disk.

5) central instance in node1 MSCS clsuter.

6)dialog instance in node2 on MSCS clsuter.

Is this correct procedure

To install the CI and DI outside of MSCS clster need to install DB2 Client software.( I understand like this suppose if we install CI and DI in another server need to install DB2 Client software).

is this correct or wrong please guide me.

Regards

Rao.

Former Member
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Hello Rao,

The sap guide has complete step-by-step installation of the cluster. If you have followed same, its perfect.

I) installed j2sdk 17 in both the nodes.

OK

2) installed DB2 in both the nodes local C drive.

> What is DB2 ?

3) Installed ASCS and SCS in virtual hostname in shared disk.

OK

4)Database instance with virtual hostname in the shared disk.

> This should be the same resource in the cluster which was created by SQL.

5) central instance in node1 MSCS clsuter.

OK

6)dialog instance in node2 on MSCS clsuter.

OK

HTH,

Kalpesh.

Former Member
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Hi

Actually I installed in DB2 database urs is SQL.

How is the insttalation? is it finshed successfully? I ame xpecting it is working fine.

How the faile over? can u give me reply.

Thanks

Answers (0)