Oracle RAC - Central or distributed SAP system

[former_member189462]

Hi experts,

We are currently working on an ugrade project and  our client requested to install the QAS system in order for them to be able to migrate it later to an Oracle RAC configuration. My main doubt here is...Must the SAP system be installed as a distributed one or we can install a central system and migrate it anyway to an Oracle RAC squema?

This is important aspect to confirm because it has impact over the resources availability.

I'm not that familiar wirh Oracle RAC and maybe this is a silly question. Sorry for that.

Thanks and regards

[Former Member]

Must the SAP system be installed as a distributed one or we can install a central system and migrate it anyway to an Oracle RAC squema?

Both is possible, but in my opinion running the database on RAC without having a standalone ASCS + ERS is rather pointless. You eliminate the database as SPOF, but you don't do it for the SAP system? I know there are other opinions out there and they may have valid reasons.

It is all about your motivation and your system design.

Cheers Michael

[former_member189462]

Thanks all for your help

It became clear to me now that both alternatives (central or distributed SAP systems) are possible. After checking with our client, the target schema will be a distributed SAP system with Oracle RAC, but they wanted to know if at this stage a central SAP system installation could be possible since they don’t have yet an extra server for a distributed SAP system. Once the upgrade project we are currently working on is finished, the migration to an Oracle RAC squema with a distributed SAP system will be the done.

Considering the above mentioned and even when possible, the best approach would be go to a distributed SAP system from the beginning. If we don’t do that...an extra step (system copy) would be required in order get a distributed SAP System and after that perform all neccessary steps to get an Oracle RAC scenario. Is my assumption correct?

Thanks again for all your help

Regards

[Former Member]

You got most of it right, but a system copy won't be necessary to transform from central to distributed.

It is more or less only a few profile parameters and directories (file systems). But still it is much easier to directly install it the way you want it to be at the end.

I did a bunch of DVEBMGS splits to ASCS / D0x manually but nowadays the sapinst install method is the easier way to do it.

Cheers Michael

[former_member188883]

Hi Diego,

Please go through SAP notes below and the white paper on Oracle RAC. This should provide you with all the required information for SAP on Oracle RAC.

Note 527843 - Oracle RAC support in the SAP environment

Note 913503 - Collective Note for Oracle 9i RAC

Note 1171095 - Information about Oracle RAC 10.2

http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/808a4099-f228-2d10-a69f-b3d37c72f...

This document explains all the necessary steps to configure an SAP system for Oracle 11g Release 2 Real Application Clusters.

Hope this helps.

Regards,

Deepak Kori

[former_member189462]

Hi Deepak,

Thanks for your response. I have already reviewed the mentioned notes and guide but unfortunately I'm not able to figure it out. Actually we are not going to perform the migration to an Oracle RAC environment...this will be performed in a later stage. Our current requirement only involves to install the system and as mentioned in my previous email...I not sure if the system could be installed as a central system o the starting point for an Oracle RAC must is a distributed system.

Thanks a lot for all your help

Regards

[Former Member]

In addition to valid Deepak's reply here is another white paper that explains how you can use Oracle Clusterware and SCS/ASCS for high availability - http://www.oracle.com/us/solutions/sap/sapctl-303790.pdf and SAP Note 1496927.

[former_member188883]

Hi Diego,

Below is an information from the whitepaper.

http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/808a4099-f228-2d10-a69f-b3d37c72f...

Option 1: New SAP System Install and Upgrade to Oracle 11.2.0.2

Please refer to the Install and Configuration Guides from SAP to perform a first system

installation. This installation of your SAP system will create a single instance Oracle

database. So this can be central system installation or Distributed. I shall recommend to go with Distributed to make things easier for migraiton.

There is no option available from SAP to install an Oracle RAC enabled database

directly. The migration to Oracle RAC must be performed after the initial installation of the

SAP system is completed.

Following points should be planned well before staring the SAP installation

1) Place the database files, redo log files, archive logs, control files and sapmnt files on a shared

filesystem. By doing so, there is no need to copy the data to a shared storage location for

RAC enabling later on.

2)  Installing the Oracle software in a shared filesystem . This is classified as an installation with a

"Shared Oracle Home".

3) During installation of the SAP software, the users <sid>adm and ora<sid> will be created.

With a shared filesystem, the home directory for these users can be shared among all nodes in

the cluster.

Hope this helps.

Regards,

Deepak Kori

[Former Member]

  "There is no option available from SAP to install an Oracle RAC enabled database

directly. The migration to Oracle RAC must be performed after the initial installation of the

SAP system is completed." - is not true anymore. This white paper is 2011, since that time SAPInst was changed and there is an option to install SAP system straight to clustered database, SAPinst is even can install Grid Infrastructure for you.