Moving location of REDO in Oracle

We had an issue today whereby the filer which held the REDO files for our databases had a hardware failure. As such, the partner filer took over the load but we were seeing a lot of log file sync waits and as a result application concurrency.

It was decided to move the REDO onto a less loaded filer. This is an ONLINE operation and this is how we did it:

1) New Filer Volume
The first step was to ask our storage team for a new filer volume on a less contended filer. So we had the following created.

Volume: DB_REDO_TEMP
Size: 75GB
Filer: FDC0777

2) Mount the volume onto the database node
Next step is to add the volume to fstab and to mount the volume and sort out the permissons

sudo su
vi /etc/fstab

Then amend fstab with a line for the new volume

FDC0777.data.dc1.mydomain.net:/vol/DB_REDO_TEMP      /oraredo/DB_TEMP

Next sort out the permissions so that it the folder structure is owned by oracle

mynode:/oraredo : mkdir DW2_TEMP
mynode:/oraredo : chown oracle:dba DW2_TEMP/
mynode:/oraredo : ls -ltrh
total 8.0K
drwxr-xr-x 3 oracle dba 4.0K Mar  3  2011 DB
drwxr-xr-x 2 oracle dba 4.0K Sep 12 10:17 DB_TEMP
mynode:/oraredo : mount /oraredo/DB_TEMP/
mynode:/oraredo : df -h
FDC0777.data.dc1.mydomain.net:/vol/DB_REDO_TEMP
                       72G  128K   72G   1% /oraredo/DB_TEMP
mynode:/oraredo : ls -l
total 8
drwxr-xr-x 3 oracle dba  4096 Mar  3  2011 DW2
drwxr-xr-x 3 root   root 4096 Sep 12 10:17 DW2_TEMP
mynode:/oraredo : chown oracle:dba DB_TEMP/
mynode:/oraredo : ls -l
total 8
drwxr-xr-x 3 oracle dba 4096 Mar  3  2011 DB
drwxr-xr-x 3 oracle dba 4096 Sep 12 10:17 DB_TEMP

The work from the O/S perspective is now done.

3) Create the new redo groups and members

The current setup was 3 groups with 2 members in each group. We wanted to maintain the same structure so the following SQL was run:

ALTER DATABASE ADD LOGFILE GROUP 4 ( '/oraredo/DB_TEMP/redo4a.log', '/oraredo/DB_TEMP/redo4b.log') SIZE 3072M;
ALTER DATABASE ADD LOGFILE GROUP 5 ( '/oraredo/DB_TEMP/redo5a.log', '/oraredo/DB_TEMP/redo5b.log') SIZE 3072M;
ALTER DATABASE ADD LOGFILE GROUP 6 ( '/oraredo/DB_TEMP/redo6a.log', '/oraredo/DB_TEMP/redo6b.log') SIZE 3072M;

This created groups 4,5 & 6, eahc with 2 members.

4) Remove the old log groups

We did this in Toad, using the Redo Log Manager.

image

We removed log groups 1, 2 & 3 when they became Archived (YES) and status of INACTIVE. To speed up the log switching process we did a manual log switch in Grid Control:

image

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