Can Oracle SE2 RAC works with only a single instance? Is it recommended

oracleoracle-12crac

I've got a client with an Oracle DB 12 SE2 RAC with two instances.

One of the instances is giving too much problems. He wants just to remove it, and therefore leaving Oracle RAC running in only with one node.

Is the client forced to convert its DB to RAC ONE NODE or to Single Instance?

Regards!

Best Answer

You can just simply shutdown and disable one of the instances.

RAC One Node is optional in this case. If you want to use features like online database instance migration or rolling patching, you may use it, this is a simple configuration change, there is nothing to be converted.

Keep in mind, while RAC and RAC One Node are available without extra cost with SE2 in 12c, starting with 19c, these options are not available anymore in Standard Edition (SE2).

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Just from Oracle side there is nothing to worry about. You could even do this operation during normal business hours.

BUT! most Applications are not cluster ready. They cannot deal with this situation and will crash. All services are still available since they are migrated to the second node. But the session does not get migrated that's why the client will loose the connection. An application which supports RAC would then reopen the connection and just continue to work.

I would plan a downtime for this operation.

For the future you could bond two network ports for the public interface in failover mode. With that setup you could do the operation without downtime. Note that bonding in load balance mode does not work so well -- at least this is my experience.

Oracle RAC – Meaning of cluster_database TRUE/FALSE

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