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Node and Instance in Oracle RAC
Hi ,
Can someone explain the below concept of instance and node in Oracle RAC with example?
An instance can access one and only one database. With Oracle RAC, there are multiple instances for one database. Each instance runs on a separate database server, called a node in the cluster
Regards,
Balaji
Best Answer
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node = host, server
instance = database instance running on a node
in a RAC database you've got multiple database instances (which are running on different nodes) which use the same database (=set of datafiles on shared storage)
There's a nice Oracle Documentation on that:
https://www.oracle.com/webfolder/technetwork/tutorials/architecture-diagrams/19/rac/main.html
HTH
Markus
Answers
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node = host, server
instance = database instance running on a node
in a RAC database you've got multiple database instances (which are running on different nodes) which use the same database (=set of datafiles on shared storage)
There's a nice Oracle Documentation on that:
https://www.oracle.com/webfolder/technetwork/tutorials/architecture-diagrams/19/rac/main.html
HTH
Markus
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Thanks Markus for your explanations along with link.
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Hi Markus,
The database instance can be relocated to another node in the cluster while maintaining application continuity.
Could you please explain this sentence? To me only users will be relocated to another surviving node when the current node is down.
Regards,
Balaji
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Hi Markus,
https://www.oracle.com/webfolder/technetwork/tutorials/architecture-diagrams/19/rac/main.html
The above link is for Oracle Real Applications Cluster 19c Technical Architecture. Similarily can you send the link for Oracle11g or 12c.
Regards,
Balaji
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Hi,
taking the general architecture, there are no major differences between RAC in 11g, 12c, 18c and 19c.
If you want to know more about the differences between the versions you mentioned, please check the Oracle documentation:
https://docs.oracle.com/en/database/oracle/oracle-database/index.html
HTH
Markus
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Basically, not "users" but "user sessions" are moved to the other node.
Application continuity takes care that no statements are lost.
For more information, please see https://www.oracle.com/database/technologies/high-availability/app-continuity.html
HTH
Markus
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Hi Markus,
If you want to know more about the differences between the versions you mentioned, please check the Oracle documentation:https://docs.oracle.com/en/database/oracle/oracle-database/index.html
You have shared Oracle database link. Kindly send Oracle RAC.
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There's a link "Clustering" ...
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May I know where can I find that link
Regards,
Balaji
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The database instance can be relocated to another node in the cluster while maintaining application continuity. Could you please explain this sentence? To me only users will be relocated to another surviving node when the current node is down.
In admin-managed RAC databases, which most of today's Oracle DBAs use, an instance cannot be relocated to another node in the cluster. The sessions can failover to another instance on another node, as already discussed, but the instance on the downed node is not moved.
If you use policy-managed RAC databases, then the instance can move to another node in the same server pool.
Cheers,
Brian