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Oracle database control file

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Written by Amal
Tuesday, 06 May 2008

ORACLE DATABASE CONTROL FILE

An Oracle database is made up of control files, data files, online redo logs, and archived redo logs which can be collectively called as physical files that make up the logical Oracle database. CONTROL FILES : A control file in oracle database is a physical file (binary) which stores the information like (list of all is provided in the end) name of the database, character set used, name of all data files and the redo log files. The location of these files is specified in the init parameter file of the oracle. When a database is mounted Oracle uses the information stored in the control file and this file is also used for database recovery.

Every Oracle database has at least one control file. If a database has multiple control files, then they are all identical to each other. Control files also contain synchronization information used during recovery from a crash or media failure.

If you lose control file for the database, you lose the entire database. For this reason, an Oracle database will typically have multiple control files located on separate physical devices. Since control files are relatively small and incur little I/O, there is no reason not to use multiple control files.

A control file consists of following information

• ARCHIVED LOG (reusable)
• BACKUP CORRUPTION (reusable)
• BACKUP DATAFILE (reusable)
• BACKUP PIECE (reusable)
• BACKUP REDOLOG (reusable)
• BACKUP SET (reusable)
• BACKUP SPFILE
• CKPT PROGRESS
• COPY CORRUPTION (reusable)
• DATABASE
• DATAFILE
• DATAFILE COPY (reusable)
• DATAFILE HISTORY
• DATABASE INCARNATION
• DELETED OBJECT (reusable)
• FILENAME
• FLASHBACK LOG
• INSTANCE SPACE RESERVATION
• LOG HISTORY (reusable)
• MTTR
• OFFLINE RANGE (reusable)
• RECOVERY DESTINATION
• REMOVABLE RECOVERY FILES
• RMAN STATUS
• RMAN CONFIGURATION
• REDO THREAD
• REDO LOG
• TABLESPACE
• TEMPORARY FILENAME
• THREAD INSTA