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Lesson 3Database control file introduction
ObjectiveDiscuss the use of database control files.

Database Control File

The control file contains information about all the files associated with your Oracle database. This is one of the files read during the startup of your instance to help determine the integrity of your database. If your database's control file is corrupt, the database cannot be mounted. If your database starts, you know your control file is good.
Recovering your database is very difficult without a good control file, so it is highly recommended that you maintain multiple copies of your control file and store each one on separate drives with separate controllers. You should also make sure the control file(s) are backed up on a regular basis. If your only control file becomes corrupted, recovery becomes more difficult. We will cover the process of multiplexing your control files later in this lesson.

Control file sections

The control file is broken down into 17 sections (12 more than Oracle7.) This is a binary file and can not be viewed or directly modified using a standard editor. Among other things, a control file contains information such as:
  1. The names and locations of associated data files and online redo log files
  2. The log history
  3. Archived log information
  4. Backup set and backup piece information
  5. Backup data file and redo log information
  6. The current log sequence number
  7. Checkpoint information

You will not be tested during the OCP exam on the different sections of the control file. You should know that it contains information about the above sections and that this information is updated on a regular basis. I will indicate when the control file is being updated where appropriate.
The next lesson is about control file maintenance.