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Mirror Oracle redo log files



Disclaimer: Apply to a TEST environment first. Use on production systems is at DBAs own risk.

This document guides you through the steps necessary to mirror Oracle database redo logs files.
Assuming that you currently have redo logs group 1, 2 and 3. Verify by using the following
query:
set linesize 130
select * from v$log;

1) alter database backup controlfile to trace;
=================================

2) Create new groups:
=====================
alter database add logfile group 4
(‘/u01/oradata/emrep/redo04.log’, ‘/u02/oradata/emrep/redo04.log’) size 100M;

alter system switch logfile;
–>until you get to group 4.

set linesize 130
select * from v$log;
–> Make sutre group 1,2 and 3 are not active before you drop them
3)Drop current redo:
====================
alter database drop logfile group 1;
alter database drop logfile group 2;
alter database drop logfile group 3;
Go to OS and delete corresponding files to log group 1, 2 and 3. Be extremely carful not to
delete the wrong files.
4) Add mirrored groups:
====================

alter database add logfile group 1
(‘/u01/oradata/emrep/redo01.log’,'/u02/oradata/emrep/redo01.log’) size 100 M;

alter database add logfile group 2
(‘/u01/oradata/emrep/redo02.log’,'/u02/oradata/emrep/redo02.log’) size 100 M;

alter database add logfile group 3
(‘/u01/oradata/emrep/redo03.log’,'/u02/oradata/emrep/redo03.log’) size 100 M;


alter system switch logfile;
select * from v$log;
–>Make sure all groups are there and mirrored.

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