Redo Log Files
The Oracle server needs a minimum of two online redo log file groups
The maximum and default value for MAXLOGMEMBERS, MAXLOGFILES is dependent on your operating system.
The minimum size of an online redo log file is 50 KB.
Adding new group:
ALTER DATABASE ADD LOGFILE GROUP 4
Adding a member in a group:
ALTER DATABASE ADD LOGFILE MEMBER
'C:\oracle\product\10.1.0\oradata\bank\REDO01a.rdo','C:\oracle\product\10.1.0\oradata\bank\REDO01b.rdo' TO GROUP 1,
'C:\oracle\product\10.1.0\oradata\bank\REDO02a.rdo' TO GROUP 2,
'C:\oracle\product\10.1.0\oradata\bank\REDO03a.rdo' TO GROUP 3;
Dropping a Redo Log Group
ALTER DATABASE DROP LOGFILE GROUP 3;
• An instance requires at least two groups of online redo log files.
• An active or current group cannot be dropped.
• When an online redo log group is dropped, the operating system files are not deleted.
Dropping Online Redo Log Members
ALTER DATABASE DROP LOGFILE MEMBER 'C:\oracle\product\10.1.0\oradata\bank\REDO03a.rdo';
• If the member you want to drop is the last valid member of the group, you cannot drop
• If the group is current, you must force a log file switch before you can drop the
• If the database is running in ARCHIVELOG mode and the log file group to which the
member belongs is not archived, then the member cannot be dropped.
• When an online redo log member is dropped, the operating system file is not deleted.