Oracle Grid Infrastructure: Active/passive Clusters

[Former Member]

Full blown RAC instances are still relatively rare. Maybe the high costs are one of the main reasons for this. Anyway, many SAP/Oracle installations don't really require a fault tolerant database. A simple automatic failover in an active/passive cluster would be sufficient.

In the book "Oracle Database 11g RAC on Linux" I found a very interessting comment on page 28:

A little known fact is that using Oracle Grid Infrastructure makes it very simple to set up a cost effective active/passive cluster. Leveraging the Grid Infrastructure API and Oracleu2019s Automatic Storage Management as a cluster logical volume manager makes it easy to constantly monitor a single instance Oracle database. In case of a node failure, the database will automatically be relocated to the standby node. Depending on the fast_start_mttr_target initialization parameter and the size of the recovery set, the failover to the standby node can be very quick; however, users will be disconnected from the database as part of the failover process.

Now I have two questions:

1. If I want to create a proof of concept, where do I start? I already had a look at the Oracle 11g documentation, but in the documentation "cluster" equals "RAC".

2. It is not sufficient to perform only a database failover. We need to handle the SAP system as well. Is it supported by SAP to put /usr/sap/SID and /sapmnt/SID into ASM 11.2 and present them e.g. as ASM cluster file systems?

Regards,

Mark

[stefan_koehler · Accepted solution]

Hello Mark,

Oracle Clusterware is a common solution for HA on Linux.

I think you are searching for this paper:

http://www.oracle.com/technetwork/database/clusterware/overview/si-db-failover-11g-134623.pdf

You can also extend, add or modify the corresponding resource groups (with SAP application part or whatever).

And to get the whole picture complete (Clusterware with RAC and Enqueue Replication for SAP):

http://www.oracle.com/technetwork/database/clusterware/overview/sap-availability-on-rac-11grel2-1704...

Regards

Stefan

[Former Member · Accepted solution]

Hello Stefan,

thanks a lot for your response! Your first link answered my question.

I know of SAPCTL, but I heard from Oracle that the use of SAPCTL is only allowed for RAC systems. Before I close this question I just wonder why the whitepaper "Using Oracle Clusterware to Protect A Single Instance Oracle Database 11g" hasn't been used as a blueprint for protecting Oracle instances e.g. on Linux? Maybe there is some license glitch which renders the option unusable?

Regards,

Mark

[Former Member · Accepted solution]

Just a short feedback from Christian Graf:

The whitepaper was only for realease 11.1, with release 11.2 this active/passive cluster is no longer supported by Oracle. You have to use RAC One Node if you want to have an active/passive cluster on release 11.2. So we'll have to wait for the availability of RAC One Node for SAP, which is on the agenda. Maybe 2012 we'll see RAC One Node supported by SAP.

[stefan_koehler · Accepted solution]

Hello Mark,

yes RAC one is recommended by Oracle, but you can achieve (nearly) the same result with 11g R2 too:

http://blogs.oracle.com/xpsoluxdb/entry/clusterware_11gr2_setting_up_an_activepassive_failover_confi...

Regards

Stefan

[Former Member · Accepted solution]

Hello Stefan,

we are both on one line. I would also prefer a simple active-passive cluster setup to a full blown RAC or even a RAC One Node. especially if the license fee for Clusterware is significantly lower than for RAC. However, Oracle staff makes it really clear that Oracle does not want customers to implement active-passive clusters based on Clusterware without RAC. They even say this active-passive cluster is no longer supported on 11.2. by Oracle! Of course it worked fine with 11.1 and there is no reason why it should be technically no longer possible with 11.2. WIth this adverse winds from Oracle blowing in our face, it doesn't make sense to implement such a active-passive cluster any more, however elegent it might have been technically.

So let's see what the alternatives are and when RAC One Node will be available (and at what price!).

Regards,

Mark

[Former Member]

Hi Mark,

>> It is not sufficient to perform only a database failover. We need to handle the SAP system as well. Is it supported by SAP to put /usr/sap/SID and /sapmnt/SID into ASM 11.2 and present them e.g. as ASM cluster file systems?

I didn't tested but I heared that there are some implementations SAP installations over acfs. Please check the note 1550133 - Oracle Automatic Storage Management (ASM) and find statement;

In ACFS the following types of files/data can be stored:

Oracle RDBMS Software (Oracle homes)
Server Parameter Files (SPFILEs) and backups of SPFILEs (pfile)
TDE Encryption Wallets
SAP software

Best regards,

Orkun Gedik