||Oracle Tips by Burleson
Chapter 5 - Oracle Database
OCP Instructors Guide for
Oracle DBA Certification
Resizing Redo Logs
The administrator’s guide states that each database should have at
least three groups of redo logs with each group having at least two
members each. In addition, Oracle recommends that all redo log group
members be the same size.
If your redo log sizes are too small (or too
large), they can be easily resized while the database is up and
running. The steps to resize the redo logs are as follows:
Determine how quickly the logs are switching by
checking the database’s alert log or the v$log_history view.
Create a dummy redo log group containing one
member. The size of the redo log group member should be large enough
to give you enough time to complete the alterations below. 15 to 30
minutes should be enough time.
Use the ALTER SYSTEM SWITCH LOGFILE statement
to make the dummy the active log group. Use the view v$log to determine which group is active. Keep switching
and checking until the dummy group becomes active.
Drop the first redo log group (ALTER DATABASE
DROP LOGFILE….) and then recreate the redo log group (ALTER DATABASE
ADD LOGFILE….). If you try to drop a group that has become active
for whatever reason, rest assured that Oracle is smarter than you
are in this case and will prohibit you from doing so.
Repeat the previous step until all of the
permanent redo log groups have been resized.
Drop the dummy log group by executing the ALTER
DATABASE DROP LOGFILE… statement.
All of the Oracle certification tests will have
numerous questions on redo logs. Test candidates should have a
strong knowledge of redo and archived redo logs including:
The above text is
an excerpt from:
OCP Instructors Guide for Oracle DBA Certification
A Study Guide to Advanced Oracle Certified Professional Database
by Christopher T. Foot
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