April 1999
Intermediate to advanced
584 pages
23h 17m
English
Content preview from Oracle Database Administration: The Essential RefeBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Control files
Every Oracle instance must have one or more control files. The control file is a binary file that is critical to Oracle, but is not directly readable by a user, nor is it editable by a text editor. The control file can be thought of as a software “bootstrap” file; it contains information that Oracle requires to start. Information stored in the control file includes:
Names and locations of data files
Names and locations of redo log files
Information on the status of archived log files
The current redo log sequence number
Redo log information required for recovery
Backup history (Oracle8 only)
Timestamp information on the instance creation and startup/shutdown
Essential parameters specified at database creation (e.g., MAXDATAFILES)
The information stored in the control file is so critical that if the control file is lost or damaged, the only options available for recovery are either to create a new control file (assuming that the DBA has access to all pertinent information required) or to rebuild the database and restore from a backup. Because of the critical nature of the control file, Oracle allows the DBA to maintain multiple mirrored control files, as specified by the CONTROL_FILES parameter in the INIT.ORA file. For example, the following line from INIT.ORA specifies two control files:
CONTROL_FILES = (/disk00/oracle/control01.ctl,/disk02/oracle/control02.ctl)
Tip
We strongly recommend that you maintain multiple mirrored control files on separate disks in case disk failure ...
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