The read-only tablespace is a tablespace that does not allow any updates or creations of new objects in the tablespace.
Read only tablespaces or system tablespaces:
Eliminates the need to perform backups again and again;Only one single backup is enough after making the tablespaces read only.
Recovery becomes easier
A read only tablespace has less overhead compared to updateable tablespace.
Readonly tablespaces can be moved to read only media devices.
When recovering read only or system tablespace there are some special considerations that should be take care of :
When a back up control file is used for media recovery you may encounter some error messages due to the read-only tablespace. The simplest solution could be is to take the data files of the read-only tablespace offline prior to the recovery.
Generally, one backup is necessary after a tablespace has become read-only as no update is being done to tablespace after this point.
If you change the status of a tablespace back to read-write then you must perform normal scheduled backups for all the datafiles associated with that tablespace.
When you change the tablespace to read-only, the control file gets updated. It is important that the control file accurately identify read-only tablespaces when performing a recovery else control file needs to be recreated.
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