Every Oracle database has a control file containing the operating system filenames of all other files that constitute the database. The control files record crucial information such as -
Without these files, the database cannot start up. If anything happens to the control files while the database is running, the database will crash. If the physical makeup of the database is altered (for example, if a new datafile or redo log file is created), then the control file is automatically modified by Oracle to reflect the change.
Oracle (or Oracle users can) multiplex the control file, allowing Oracle to write multiple copies of the control file to protect it against disaster or failure.
If the operating system supports disk mirroring, the control file can also be mirrored, allowing the O/S to write a copy of the control file to multiple disks. Every time a user mounts an Oracle database, its control file is used to identify the datafiles and online redo log files that must be opened for database operation.
The control file should be backed up whenever the structure of the database changes. Structural changes can include adding, dropping, or altering datafiles or tablespaces and adding or dropping online redo logs.
- Database name,
- Timestamp of database creation,
- Names of the database's Datafiles and online and archived redo log files,
- Datafile locations,
- Checkpoint, a record indicating the point in the redo log where all database changes prior to this point have been saved in the datafiles
- Synchronization information, and
- Recovery Manager(RMAN) backup meta-data
Without these files, the database cannot start up. If anything happens to the control files while the database is running, the database will crash. If the physical makeup of the database is altered (for example, if a new datafile or redo log file is created), then the control file is automatically modified by Oracle to reflect the change.
Oracle (or Oracle users can) multiplex the control file, allowing Oracle to write multiple copies of the control file to protect it against disaster or failure.
If the operating system supports disk mirroring, the control file can also be mirrored, allowing the O/S to write a copy of the control file to multiple disks. Every time a user mounts an Oracle database, its control file is used to identify the datafiles and online redo log files that must be opened for database operation.
The control file should be backed up whenever the structure of the database changes. Structural changes can include adding, dropping, or altering datafiles or tablespaces and adding or dropping online redo logs.
