Donald K. Burleson
Oracle Export Files
Export files affect the recoverability
of your database should some disaster befall it. Export files,
created by the export utility supplied by Oracle, are copies of a
database’s data and structure at a given point in time. Export files
are logical copies of the database, not physical copies. Several
types of exports will be covered in Chapter 15. Export files should
be stored in a separate location from archive files.
Oracle Archive Log files
Archive logs, as stated previously, are archived copies of the redo
logs. They provide the capability to recover to a specific point in
time for any tablespace in the database. For any application
considered to be production- or mission-critical, archive logging
must be turned on. These files can be stored to disk, tape, or even
optical storage such as WORM (write once, read many). Using
operating system backups such as COPY on NT or W2K, or TAR on UNIX,
and with the application of archive logs, a database can be
recovered quickly after disaster. Archive logs can only be used to
recover when cold or hot backups are used for Oracle backup. Archive
logs cannot be applied to a recovery using exports files.
After each successful hot or cold backup of an Oracle database, the
associated archive and backup files may be removed and either placed
in storage or deleted. In an active database archive, logs may
average tens of megabytes or gigabytes per day. Clearly, storage for
this amount of data needs to be planned for; for example, at one
installation doing Oracle development with no active production
databases, gigabytes of archives and a like amount of exports were
generated in a one-week period. If archive logging is turned on and
you run out of archive disk space, the database stops after the last
redo log is filled. Plan ahead and monitor disk usage for instances
using archive logging.
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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