- Controlfiles
- Datafiles
- Online Redo log files
With default installation, Oracle has 3 control files placed in same physical location. According to database availability, It is safe to place the 3 controlfiles in disk.
To see the current physical location of control file
SQL> select name from v$controlfile;
NAME
---------------------------------------------------------
/ua1/control01.ctl
/ua1/control02.ctl
/ua1/control03.ctl
Suppose we have two HD and those two are mount as /ua1 and /ua2. So we need to move at list one controlfile in /ua1 and we move the 3rd contronlife. there are several way to do the Control File Multiplexing:
1. Using SPFILE:
The steps to multiplex control files using an SPFILE are describe bellow:
Login as SYSDBA
1. Alter the SPFILE: Using the ALTER SYSTEM SET command, alter the SPFILE to include a list of all control files to be used.
SQL> ALTER SYSTEM SET control_files='/ua1/control01.ctl'
,'/ua1/control01.ctl', '/ua1/control01.ctl' scope=spfile;
2. Shut down the database: Shut down the database in order to create the additional/ relocate control files on the operating system.
SQL> SHUTDOWN IMMEDIATE;
3. Create additional control files: Using the operating system copy command, create/move the additional control files as required and verify that the files have been created in the appropriate directories.
mv /ua1/control01.ct /ua2
4. Start the database: When the database is started the SPFILE will be read and the Oracle server will maintain all the control files listed in the CONTROL_FILES parameter.
SQL>STARTUP;
To see the changed physical location of control file
SQL> select name from v$controlfile;
NAME
---------------------------------------------------------
/ua1/control01.ctl
/ua1/control02.ctl
/ua2/control03.ctl