Oracle7 Server Administrator's Guide

Dropping Online Redo Log Members

In some cases, you might want to drop one or more specific online redo log members. For example, if a disk failure occurs, you might need to drop all the online redo log files on the failed disk so that Oracle7 does not try to write to the inaccessible files. In other situations, particular online redo log files become unnecessary; for example, a file might be stored in an inappropriate location.

To drop an online redo log member, you must have the ALTER DATABASE system privilege.

Consider the following restrictions and precautions before dropping individual online redo log members:

It is all right to drop online redo log files so that a multiplexed online redo log becomes temporarily asymmetric. For example, if you use duplexed groups of online redo log files, you can drop one member of one group, even though all other groups have two members each. However, you should rectify this situation immediately so that all groups have at least two members, and thereby eliminate the single point of failure possible for the online redo log.

An instance always requires at least two valid groups of online redo log files, regardless of the number of members in the groups. (A group is one or more members.) If the member you want to drop is the last valid member of the group, you cannot drop the member until the other members become valid; to see a redo log file's status, use the V$LOGFILE view. A redo log file becomes INVALID if Oracle7 cannot access it. It becomes STALE if Oracle7 suspects that it is not complete or correct; a stale log file becomes valid again the next time its group is made the active group.

You can drop an online redo log member only if it is not part of an active group. If you want to drop a member of an active group, first force a log switch to occur.

Make sure the group to which an online redo log member belongs is archived (if archiving is enabled) before dropping the member. To see whether this has happened, use the Server Manager ARCHIVE LOG command with the LIST parameter.

To drop specific inactive online redo log members, use either the Drop Logfile Member menu item of Server Manager, or the SQL command ALTER DATABASE command with the DROP LOGFILE MEMBER clause.

The following statement drops the redo log LOG3C:

ALTER DATABASE   DROP LOGFILE MEMBER 'log3c';

When an online redo log member is dropped from the database, the operating system file is not deleted from disk. Rather, the control files of the associated database are updated to drop the member from the database structure. After dropping an online redo log file, make sure that the drop completed successfully, and then use the appropriate operating system command to delete the dropped online redo log file.

See Also: For information on dropping a member of an active group, see "Forcing a Log Switch" .