When a node generates an archived redo log, Oracle Database always records the file name of the log in the control file of the target database. If you are using a recovery catalog, then RMAN also records the archived redo log filenames in the recovery catalog when a resynchronization occurs.
The archived redo log naming scheme that you use is important because when a node writes to a log with a specific file name on its file system, the file must be readable by any node that must access this archived redo log. For example, if node1 archives a log to /oracle/arc_dest/log_1_100_23452345.arc, then node2 can back up this archived redo log only if it can read /oracle/arc_dest/log_1_100_23452345.arc on its own file system.
The backup and recovery strategy that you choose depends on how you configure the archiving destinations for each node. Whether only one node or all nodes perform archived redo log backups, you must ensure that all archived redo logs are backed up. If you use RMAN parallelism during recovery, then the node that performs recovery must have read access to all archived redo logs in your cluster.
Multiple nodes can restore archived logs in parallel. However, during recovery, only one node applies the archived logs. Therefore, the node that is performing the recovery must be able to access all of the archived logs that are needed for the recovery operation. By default, the database determines the optimum number of parallel threads to use during the recovery operation. You can use the PARALLEL clause in the RECOVER command to change the number of parallel threads.
Guidelines and Considerations for Archived Redo Logs
The primary consideration is to ensure that all archived redo logs can be read from every node during recovery, and, if possible, during backups. During recovery, if the archived log destinations are visible from the node that performs the recovery, then Oracle Database can successfully recover the archived log data.