Redo Log File Storage in Oracle RAC

Learn about redo log requirements for Oracle Real Application Clusters (Oracle RAC) databases.

In an Oracle RAC database, each instance must have at least two groups of redo log files. When you use Oracle DBCA to create the database, Oracle DBCA allocates redo log files to instances, as required, automatically. You can change the number of redo log groups and the size of the redo log files as required either during the initial database creation or as a post-creation step. If you add a node to the cluster, then the addNode script configures the redo logs on the new server.

When the current group fills, an instance begins writing to the next log file group. If your database is in ARCHIVELOG mode, then each instance must save filled online log groups as archived redo log files that are tracked in the control file. During database recovery, all enabled instances are checked to see if recovery is needed. If you remove an instance from your Oracle RAC database, then you should disable the instance's thread of redo so that Oracle does not have to check the thread during database recovery.