I. Control Files
- The control file is a relatively small file (up to 64 MB ). The parameter file informs the instance of the control file location, and the control file informs the instance database and the online redo log file location.
- The control file also informs oracle of some things, such as information about checkpoints and database names (must match the db_name parameter) create a database timestamp, archive redo log history (sometimes this will make the control file larger), RMAN information and so on.
Ii. redo log files
- Redo log files are critical to Oracle databases. They are the transaction logs of the database.
- Purpose
- Instance recovery after system crash
- Restore media after data files are restored through backup
- Backup database processing
- Input to the stream. This is a redo log mining process for information sharing.
- Redo log files: online and archived logs
3. Online log files
- Each Oracle database has at least two online redo log file groups. Each redo log group contains one or more redo log members, the individual redo log file members of these groups actually form an image of each other. The size of these online redo log files is fixed and used cyclically.
Switching from one log file group to another is called Log switching.
