MULTIPLEXING and ARCHIVING Redo Logs

[quester]

I am really confused between MULTIPLEXING redo log files and ARCHIVING redo log files. I know the process is different, but isn't the application same.

I mean when we can have multiple copies by MULTIPLEXING, why do we then need to ARCHIVE also? Kindly clarify my confusion.

[Parikshit]

Multiplexing redo log files means several copy of
the same log files are kept in different locations
which will be simultaneously updated at any point
of time. But archiving is something different ....
Archiving redo log files is u are keeping track of the permanent changes done in the database into some
files. The redo log files will be overwritten when
check point arrives. But archived files are not
overwritten and they can be used for database
recovery if the database crashes.

[quester]

Originally posted by Parik****
Multiplexing redo log files means several copy of
the same log files are kept in different locations
which will be simultaneously updated at any point
of time. But archiving is something different ....
Archiving redo log files is u are keeping track of the permanent changes done in the database into some
files. The redo log files will be overwritten when
check point arrives. But archived files are not
overwritten and they can be used for database
recovery if the database crashes.

So does it mean that multiplexed files cannot be helpful for recovery?

[Tarry]

By multiplexing you make sure that a disk failure will not prevent your db to go down, you'll have the same redo logs on other disk.