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What is control file?

Every Oracle database has a control file, which is a binary file containing information about the physical structure of the database, such as the names and locations of a database's datafiles and redo log files. Every time an instance of the database is started, its control file is used to identify the database and redo log file that must be open for the database to run properly. Each time the physical structure of the database is changed, for example a new datafile is added, the control file is automatically modified with the change. As you learned in the previous modules, a control file is also used if a database recovery becomes necessary. If you lose all the control files due to a media failure, you need to recreate them. There are, however, other situations that require you to recreate the control file:

Change Database Name

  1. The current database name needs to be changed

This would happen if the current database becomes a part of the distributed database system and the name for the current database name already exists in the system.
  1. The current settings in the control file need to be changed

Once the control file is created, the value for some of the settings, like MAXDATAFILES or MAXLOGMEMBERS, cannot be changed dynamically. If you need to change these settings, you need to recreate the control file.