Multiplexing Redo log File

Multiplex redo log by adding group:

Redo log files are used to record changes made to the database. Redo log files are important for the recovery purpose.So thats why in some cases you might need to create additional log file groups. To create a new group of online redo log files use the following SQL command:
Alter database add logfile group 3 ('/opt/luck/redo03_00.log',
'/opt/luck/redo03_01.log') size 10m;

Multiplexing redo log by adding member:

You can add new members to existing redo log file groups using the following ALTER DATABASE ADD LOGFILE MEMBER command:

Alter database add member '/opt/luck/redo02.log' to group 1,

'/opt/luck/redo02.log' to group 2,

'/opt/luck/redo03.log' to group 3;

Use the fully specified name of the log file members; otherwise the files are created in a default directory of the database server. If the file already exists, it must have the same size, and you must specify the REUSE option.