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Re: Concepts question about Redo Log Files

From: Mike Perrien <mperrien_at_bellsouth.net>
Date: 1997/01/06
Message-ID: <01bbfc02$9299aea0$4b0c35cf@MPERRIEN>#1/1

Paul,

The set of redo log files for a database is collectively known as the database's redo log. The primary function of the redo log is to record all changes made to data. Should a failure prevent modified data from being permanently written to the datafiles, the changes can be obtained from the redo log and work is never lost.

Redo log files are critical in protecting a database against failures. To protect against a failure involving the redo log itself, Oracle allows a multiplexed redo log so that two or more copies of the redo log can be maintained on different disks.

The information in a redo log file is used only to recover the database from a system or media failure that prevents database data from being written to a database's datafiles.

Sincerely,

Michael Perrien
Staff Consultant
Oracle Government Services, Southeast Region

Paul <bfekrat_at_erols.com> wrote in article <32CD9B41.6EB3_at_erols.com>...
> Could someone please explain to me the reason we must have redo log
> files? That is, why can't we just write committed transactions directly
> to the data files?
>
> I understand the importance of multiplexing the redo log files for
> backup and recovery issues. I also can see how a small, sequential redo
> log file might be written to by Oracle, slightly faster than the actual
> data file. But I just don't see why, in theory, we couldn't do away
> with the redo log files. Someone please help explain this to me as I
> will not be able to sleep until I fully understand WHY!!!!!!
>
> Paul
>
  Received on Mon Jan 06 1997 - 00:00:00 CST

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