Thursday, July 21, 2011

Using Enterprise Manager Database Control for a RAC cluster

A friend wrote:
We are using 11GR2 RAC with 5 nodes on Redhat Linux;

We have configured the DB coonsole (not grid control) to run in Node 1 as repository and active node and the agents to run in nodes 2, node 3, node 4 and node 5.

We have used this command to configure that;

emca -config dbcontrol db -repos create -cluster -EM_NODE db01 -EM_NODE_LIST db02,db03,db04,db05

Now, in order to be prepared in the case of failure of our node 1, I have to prepare the procedure in order to maybe move the repository (the same node 1 repository) to run in node 2 actively and the agents to run in node 3, node 4 and node 5.

I would like to keep the node 1 repository but moving it to node 2, and run node 2 as the active node, in case of failure just to guarantee the HA.


Please let me know if it's clear now. I wonder if you could give a help and help guide me in order to have the procedure prepared,
My reply to him:

Oracle really recommends using a separate installation of Enterprise Manager Grid Control for RAC databases, and then putting agents on all RAC nodes. That way you are covered for any node failure, Enterprise Manager will keep on working.

For what you want, ie. using EM Database control and then failing over Database Control from 1 RAC node to the other, it is not recommnended but it is possible, please use these commands:

Drop the DB Control on all RAC nodes, but keeping the repository. Run this command on the first node: (in the second iteration, try it on a different node)

$ emca -deconfig dbcontrol db -cluster
Enter the following information:
- Database unique name

This emca command does the following:
- stop the DB Control (dbconsole, agent) on all nodes of the cluster
- remove all DB Control related directories on all nodes of the cluster

The repository is in the RAC database and has not been dropped. You can then recreate the DBControl without recreating the repository. Do this by:

emca -reconfig dbcontrol -cluster -EM_NODE db02 -EM_NODE_LIST db01,db03,db04,db05

Test out the above and let me know if ok.

For added info please see the My Oracle Support (MOS) note "How to manage DB Control 11.x for RAC Database with emca" [ID 578011.1]

Regards,

Porus.

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