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Oracle Tips by Burleson |
Oracle Control Files
An Oracle database cannot be started without at least one Oracle control
file.
The Oracle control file contains data on system structures, log
status, transaction numbers, and other important information about
the database.
When tools such as Oracle’s RMAN backup tool are used,
the Oracle control file can be several tens of megabytes in size. It is
wise to have at least two copies of your Oracle control file on different
disks, three copies of Oracle control files for OFA compliance. Oracle will maintain them as mirror
images of each other. This ensures that loss of a single Oracle control
file will not knock your database out. You should not
bring a Oracle control file back from a backup, even though this is
supported; the Oracle control file is a living file that corresponds to current database
status. In Oracle, there is a CREATE CONTROL
FILE command that allows recovery from loss of a Oracle control file.
However, you must have detailed knowledge of your database to use it
properly.
There is also an ALTER DATABASE BACKUP CONTROL FILE TO
TRACE command that creates a script to rebuild your Oracle control file.
In Chapter 15, Backup and Recovery Procedures for Oracle, the section
titled “Backup and Recovery Plans for Oracle,” explains in detail how to protect yourself from the loss of an
Oracle control file. It is
easier to maintain extra Oracle control file copies.
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