Every Oracle Database has a control file, which is a small binary file that records the physical structure of the database. The control file includes:
The database name
Names and locations of associated datafiles and redo log files
The timestamp of the database creation
The current log sequence number
Checkpoint information
The control file must be available for writing by the Oracle Database server whenever the database is open. Without the control file, the database cannot be mounted and recovery is difficult.
The control file of an Oracle Database is created at the same time as the database. By default, at least one copy of the control file is created during database creation. On some operating systems the default is to create multiple copies. You should create two or more copies of the control file during database creation. You can also create control files later, if you lose control files or want to change particular settings in the control files.