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Multiplexing The Oracle Control File

January 16, 2008

One of the basic tasks of a DBA is to multiplex the Control Files. One of the biggest reasons why we multiplex control files is to create backups of the primary control file, which “records the physical structure of the database.” When the control file is damaged there is no way you can bring it back to life, unless you have the backup. Backup of control files must also be stored in a different physical disk for high availability. Of course, we’re very much aware that there is such a thing as “disk failure”. The Control File should always be multiplexed/backed up, as a best practice, each time that Tablespaces and Redo Log Files are dropped or added. This is also done when a datafile is renamed.The following is a quick step-by-step for multiplexing the Control File:

Suppose our SID is called ORCL,

1. Connect to the ORCL Database as SYS (SYSDBA priveleges), then EXECUTE a SHUTDOWN IMMEDIATE command

2. Locate the Control File named CONTROL1.CTL (\oracle\product\10.2.0\oradata\ORCL\control01.ctl)

3. Copy the Control File into a different location (different disk); and rename the copied file with the next number suffix (CONTROL03.CTL, if you already have CONTROL01.CTL & CONTROL02.CTL). Oracle Databases should at least have two (2) Control Files.

4. Open the initialization file, initSID.ora (which in our sample is initORCL.ora, following the standards of best practices in object naming). The initialization file is located in ORACLE_BASE\Admin\ORCL\pfile directory (OFA compliant).

5. Add the new, copied file onto the initialization parameter file The new control file is in the “D” drive:

control_files=

(

“C:\oracle\product\10.2.0\oradata\ORCL\control01.ctl”,

“C:\oracle\product\10.2.0\oradata\ORCL\control02.ctl”,

“D:\oracle\product\10.2.0\oradata\ORCL\control03.ctl”

)

6. Close and Save the file; and restart the Database using STARTUP command (MOUNT mode) with the PFILE parameter.
[Posted in DB Technology > Oracle]

-Marlon Ribunal

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