Moving RAC redo log files in ASM

 

By Kamran Agayev:

Question:  I need to move my redo loog files in RAC under ASM from one location to another.  How do I move redo ogs under ASM in a RAC environment?

Answer:  Here're the steps you need to perform in order to move redo log files to the different ASM diskgroup in a RAC environment

First of all, make sure you've been provided shared disks by system administrators. If you're using asmlib, create the disks using oracleasm as follows, using the oracleasm create command:

[oracle@node1 ~] sudo /etc/init.d/oracleasm createdisk RLOGS /dev/mapper/mpath6

Then run scan and query new disks from other nodes:

[oracle@node2 ~]$ sudo /etc/init.d/oracleasm scandisks
[oracle@node2 ~]$ sudo /etc/init.d/oracleasm listdisks

After having your disk added to the list, query it from /dev/oracleasm/disks folder:

[oracle@node1 ~]$ ls -ltr /dev/oracleasm/disks/

If you got the disk, then everything is ok. Now you can connect to the ASM instance and create a diskgroup. For this, get the name of the ASM instance from OS and connect to it:

ps -ef | grep ASM
export ORACLE_SID=+ASM1
sqlplus / as sysdba

SQL> create diskgroup RLOGS external redundancy
2 DISK '/dev/oracleasm/disks/RLOGS';

Diskgroup created.

If it's not mounted on the rest nodes, connect to those nodes and mount it manually:

SQL> alter diskgroup RLOGS mount;

And also make sure the name of the disk group is added to asm_diskstrings parameter at ASM instance

After having your disk group created, create new redo log group per thread, and remove on redo log group from the same thread which has INACTIVE status.  You can check the status of any group based on thread using V$LOG view:

SELECT
   group#,
   thread#,
   status
FROM
   v$log
WHERE
   thread# = 2
ORDER BY
   2, 1;

GROUP# THREAD# STATUS
———- ———- —————-
20 2 CURRENT
21 2 INACTIVE

Now add new group to the same thread (thread#=2) and check v$logfile view:

SQL> ALTER DATABASE ADD LOGFILE THREAD 2 GROUP 22 ('+RLOGS') SIZE 50M

SELECT
   lf.group#,
   lf.MEMBER
FROM
   v$logfile lf,
   v$log l
WHERE
   lf.group# = l.group#
AND
   l.thread# = 2;

GROUP# MEMBER
———- ——————————————————-
20 +OLD_LOG/PROD/onlinelog/group_20.259.815656575
21 +OLD_LOG/PROD/onlinelog/group_21.260.815656475
22 +RLOGS/PROD/onlinelog/group_22.260.815656475

Now you can safely delete INACTIVE redo log group from the same thread:

SQL> ALTER DATABASE DROP LOGFILE GROUP 21;

Perform above mentioned steps one by one for each thread.

Each time switch log file and make sure the new redo log member is used. Moreover, try to query both sql commands that are written above after each time you add and drop redo log group to see if it's added/deleted successfully.

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