The control file is a small binary file necessary for the database to start and operate successfully. Each control file is associated with only one Oracle database. Before a database is opened, the control file is read to determine whether the database is in a valid state to use. A control file is updated continuously by the Oracle server during database use, so it must be available for writing whenever the database is open. The information in the control file can be modified only by the Oracle server; no database administrator or end user can edit the control file. If for some reason the control file is not accessible, the database does not function properly. If all copies of a database’s control files are lost, the database must be recovered before it can be opened.
Contents of the Control file
A control file contains the following entries: • Database name and identifier • Timestamp of database creation • Tablespace names • Names and locations of data files and online redo log files • Current online redo log file sequence number • Checkpoint information • Begin and end of undo segments • Redo log archive information • Backup information