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Oracle Database Physical Files tutorials

  • There are three fundamental types of physical files that make up an Oracle Database.

    • Control files

    • Datafiles

    • Redo log files

Control File:

  • Every Oracle Database has a control file. File extension is .ctl

  • It 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,

  • Log history and current log sequence number,

  • Archived log information,

  • 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.



  • All of the data stored within an Oracle database must reside in a tablespace.

  • Each tablespace is composed of physical structures called datafiles.

  • File extension of datafile is .dbf

  • Oracle Database can be deployed on up to 64,000 datafiles.


Redo Log files

  • Control files identify redo log files and then record changes to datafiles.

  • Redo log files are most crucial structure for recovery operations.

  • It consists of two or more pre-allocated files, that store all changes made, to the Database as they occur.

  • Every instance of an Oracle Database, has an associated redo log, to protect the database in case of an instance failure.

  • File extension of redo log file is .rdo.

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