Donald K. Burleson
Oracle Archives – archived
Archive log files are only present if
archive logging has been initiated in the database instance. Archive
logs are copies of the filled redo logs. Archive logs are used to
provide point-in-time recovery to time-of-failure. Archive logs can
consume a large amount of disk resource in an active environment. In
some situations, I have seen archive logs consume tens of gigabytes
of disk area in a single day. I am sure there are installations
where it is normal to use hundreds of gigabytes for archive logs.
If you want to be able to recover your database to point-of-failure,
you have to use archive logging. The logs should be placed away from
the other files in the system on a physically separate disk farm, if
possible. In one situation, we had to perform an incomplete recovery
after a disk failure because the archive logs were on the same disk
farm as the other files and the failed disk had sections striped to
datafiles, redo logs, and archive logs.
It is usual to keep all archive logs since at least the last backup
in a quickly retrievable state. The storage area can be optical
storage, tape, or disk for archive logs. However, I suggest that
fast media be used for the initial site to which archive logs are
written. The use of fast media for the initial archive log location
is required to prevent waits caused by the system cycling back to
the redo log being archived before it has been written out
completely; this results in a hung database until the archive
becomes “unstuck.” Once the archive log is written out, it can then
be copied to its final location. Once a full cold or hot backup is
taken, all previous archive logs can be erased or placed in
This is an
excerpt by Mike Ault’s book “Oracle
Administration & Management”. If you want more current Oracle tips
by Mike Ault, check out his new book “Mike
Ault’s Oracle Internals Monitoring & Tuning Scripts” or
Ault’s Oracle Scripts Download.
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