RE: RAC One Node - which server does instance start on?

From: Shanmugam, Satheesh B <>
Date: Fri, 30 Nov 2012 18:22:37 +0000
Message-ID: <>

Did some poc on this sometime back. Managed to document some of my finding. Hope this gives you some info.

For installing RACONE we need to install:

1.	Grid infrastructure
2.	RAC software in all the nodes
3.	While creating DB using DBCA select RAC One node option. DBCA can be used only above In version we will have to use command line utility provided by oracle.  

Some of the issues found:
1.	This feature works best in and above. In version dataguard is not supported. Administration of RACONE in will be using command line tool. These tools are not user friendly. There is mandatory patch(#9004119) which needs to be applied to
2.	OEM 11.1 doesn’t support RACONE.  It doesn’t understand the failover or relocate option. 
3.	OEM 11.1 doesn’t recognize the racone db automatically. We will have to manually add the entries to OEM 11.1. Any failover or relocate we will have to do it manually. 
4.	Configuration type in dbca should be ‘Admin-Managed’ and not ‘Policy-Managed’
5.	When the inst_1 is running via racone, you can actually open the inst_2 in node 2. Technically we can have both the instance running. Though Inst_2 will use different service name than that of inst_1. This will confuse the DBA whether the it’s racone or not. But one good thing is all the racone instance will end with underscore and a number.

Crashing instance/node (failover):
                 When the node goes down or kill the pmon (kill -9 pmon), then cluster first tries to restart the instance in same node. If it is unsuccessful, it will start the instance in other node.  In the other node it will start with same name. Say If the instance name is inst_1, when it failover to node 2 it will be still inst_1.
                If you shutdown the db using shutdown abort/immediate, then cluster DOESN’T start the db automatically.
               The user sessions which are connected during failover will be disconnected. Users needs to open a new session.

               If you are relocating instance inst_1 from node 1 to node 2, it will create init.ora automatically in node 2. In node 2 it will start with different instance name, say inst_2.  
                The user sessions which are connected during switchover will remain connected. But any query which is running during the relocate phase will fail. User has to reissue the query.

Post switchover, it uses different instance name. In failover it retains the same instance name.


                You can convert the db from RACONE to RAC or vice versa using simple command. 

Some important commands,

srvctl relocate database -d inst_1 -n node2 –v  inst_1 relocated to node 2.

srvctl config database –d <db_unique_name>  Using this command you can figure out whether the db is RACONE or not.

srvctl convert database –d <db_unique_name> -c RAC/RACONE  Convert the db to rac or racone

Satheesh Shanmugam

-----Original Message-----

From: [] On Behalf Of Jared Still Sent: Thursday, November 29, 2012 11:03 PM To: Oracle-L Freelists
Subject: RAC One Node - which server does instance start on?

Yesterday I had my first experience with RAC One Node, and there is one feature of it that is somewhat confusing. We installed RAC One Node on an ODA, and all went smoothly.

When we started the database it appears the default node is the second node, as the database always starts on the second node.

We did use 'srvctl relocate database -d db -n new_node' to relocate the instance to node A, and that works as expected.

So, we restarted the database, using srvctl from node A.

Again the instance started on Node B.
 Googling and Oracle support haven't been helpful for this so far.  BTW, using 'start instance' with -n node or -i instance is not supported with RAC One Node.

Oracle strongly recommends that database connections are made through a service, and I suspect that is due to not knowing which node the database may be running on, All indications so far are that this is the way it works normally, but there does not seem to be a lot of experience with RAC One Node in the community.

Any ideas?

Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist Oracle Blog: Home Page:


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