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DB service concept
Hi,
A service name can be associated with multiple database instances, and an instance can be associated with multiple services. The listener acts as a mediator between the client and database instances and routes the connection request to the appropriate instance. Clients connecting to a service do not have to specify which instance they want to connect to.
Could someone please explain me this concept with example and diagram as I am confused about DB instance and instance.
Regards,
Balaji
Answers
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please correct your question what do you mean by db instance and instance?
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Hi Sunny,
This question is based on Oracle RAC.
Regards,
Balaji
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Balaji
I guess you have to understand the RAC cluster concept.
A simple example is a two node cluster. On each node there will be a set of db processes (pmon, smon, etc) that manage a db instance. So both nodes will manage the database separately. BUT the both nodes will share access to the db files in ASM.
You can create and run a service on either (or both) nodes. This allows you to connect to each node via the service. You can then direct transactions where the service is run. For example, you can have an app service running on node 1 and say a backup service on node 2. This means all app transactions would run from node 1, and backups from node 2; make sense?
The service concept is very powerful; especially for performance, availability, monitoring and patching.
Norm