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 if 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 control file is a binary file that defines the current state of the physical database..
• Loss of the control file requires recovery
• Is read at MOUNT stage
• Is required to operate
• Is linked to a single database
• Should be multiplexed
• Maintains integrity of database
• Sized initially by CREATE DATABASE

Control File Contents

The information in the control file includes:
• Database name is taken from either the name specified by the initialization parameter
DB_NAME or the name used in the CREATE DATABASE statement.
• Database identifier is recorded when the database is created.
• Time stamp of database creation is also recorded at database creation.
• Names and locations of associated data files and online redo log files are updated when
a data file or redo log is added to, renamed in, or dropped from the database.
• Tablespace information is updated as tablespaces are added or dropped.
• Redo log history is recorded during log switches.
• Location and status of archived logs are recorded when archiving occurs.
• Location and status of backups are recorded by the Recovery Manager utility.
• Current log sequence number is recorded when log switches occur.
• Checkpoint information is recorded as checkpoints are made.


Obtaining Control File Information

The SHOW PARAMETERS command can also be used to find the location of the control files.

show parameters control_files;


Information in several of the other dynamic performance views is obtained from the control

The minimum number of days that a reusable record is kept in the controlfile is controlled by the control_file_record_keep_time parameter.

These sections consist of records. The size, total number and number of used record are exposed through v$controlfile_record_section.


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