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Friday, 26 October 2012

Why can't you use RMAN to back up Online Redo Log Files

The Oracle database uses the three types of "live" files during its operation:datafiles,control files and online redo log files.Of these files RMAN only backs up the datafiles and the control files.You can't use RMAN to backup the online redo log files.
If you are operating in No-Archivelog mode,then you won't need the online redo log files ,since the database files are always consistent when you backup the database using the only permitted modes of backing up a database in No-archivelog mode,which are closed whole backups.
You won't need the online redo log backups if you are operating in Archivelog mode either ,since RMAN is continually backing up all your archived redo logs.
However you must make sure you always multiplex the online redo log so you won't lose all the members of a group.