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Converting RAC database into a single instance database [message #337802]

Fri, 01 August 2008 04:26

rolex.mp
Messages: 161
Registered: February 2007

Senior Member

I am using Oracle 10g on Linux

We have a live 2 node RAC instance and we do have a DR instance located at a different place . Now the DR instance is a single instance database and the backups of RAC instance are shipped to the DR node through snapshots ( NetApp) . The backup would consist of redo logs , archived logs , datafiles , parameter files , control files and the password files.

Now when a media failure happens at live site I need to get the DR database running but I dont know how to convert the RAC database into a single instance database?

Since we would be having a list of redo logs , undo tablespace for the other instance and these might be required when we recover the database in the DR site but since it is a single instance database I can use redo logs , undo tablespaces of only one instance ? Am I correct ? Let me know how to tackle this issue ?

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Re: Converting RAC database into a single instance database [message #337806 is a reply to message #337802]

Fri, 01 August 2008 04:35

rsreddy28
Messages: 295
Registered: May 2007

Senior Member

user RMAN as that is the method by which we convert a single instance to RAC instance and now as you want to convert RAC instance to a single instance, its the only method.

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Re: Converting RAC database into a single instance database [message #337835 is a reply to message #337802]

Fri, 01 August 2008 05:33

Mahesh Rajendran
Messages: 10708
Registered: March 2002
Location: oracleDocoVille

Senior Member
Account Moderator

RAC or NORAC , DR concepts are same.
Even in RAC you backup one instance at a time.
>>I dont know how to convert the RAC database into a single instance database?
If you are just applying logs to a pre-existing instance, nothing to convert. Oracle will identify the logs it needs ( from both primary nodes ) and apply accordingly.
During backups you are supposed to back archived logs from both instances and ship them across.
If you are creating/restoring the new single instance in case of
disaster,
then use RMAN methods to read the shipped backupsets. RMAN
By default will create
only single instance (if the DR is also RAC, you need to
add more threads to convert single instance to RAC).

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Re: Converting RAC database into a single instance database [message #337855 is a reply to message #337802]

Fri, 01 August 2008 06:24

rolex.mp
Messages: 161
Registered: February 2007

Senior Member

The Live Site is configured with ASM and the ASM volumes are shipped to DR site and when disaster occurs we use oracleasm to scan the disks .So directory structure remains the same with ASM configured in the DR site too.

Archived logs of both the instances are backed up.

So when I have all the backups ( including redo logs and undo tablespace of the second instance ) in the DR site , changing the init.ora such that the second instance parameters are removed and removing cluster_databases=true parameter too, will it not do the trick ?

I tried it and it worked but I was doubting the consistency , now my doubt is when the recovery happens will it apply the redo of both the threads and also the two instances in the Live database would have been pointing to two different undo tablespaces ?
When I set the undo_tablespace parameter in the DR site , what should I set , I did set it one of the two undo tablespaces and it did work but I dont know what I did is correct ?

[Updated on: Fri, 01 August 2008 06:40]

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Re: Converting RAC database into a single instance database [message #337921 is a reply to message #337855]

Fri, 01 August 2008 10:13

Mahesh Rajendran
Messages: 10708
Registered: March 2002
Location: oracleDocoVille

Senior Member
Account Moderator

>>removing cluster_databases=true parameter too, will it not do the trick ?
What trick are you talking about?
It just ask Oracle to consider that the said is instance to be mounted in single instance mode or non-rac mode.
You can have more than one undo tablespace in DR. Does not matter.
But for restore and further recovery, you need archives from both
primary nodes.
>>The Live Site is configured with ASM and the ASM volumes are shipped to DR site and when disaster occurs we use oracleasm to scan the disks
Interesting. I have never tried that before. Would do it and see whether it will help us any better at our shop.
I just use RMAN to do the job(restore/duplicate). Totally scripted, very consistent and handy.

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Re: Converting RAC database into a single instance database [message #343196 is a reply to message #337802]

Tue, 26 August 2008 10:52

valrossie
Messages: 1
Registered: August 2008

Junior Member

I was able to find a Doc. on metalink with step by step instructions on.How to convert a single instance Database to RAC", but not the other way round. So, I raised a TAR for this. The analyst's response from Oracle is.We cannot convert a RAC database into a Single instance database, that is the reason why you didnt find any steps. It is not supported.
-------------------------
valrossie

[Updated on: Tue, 26 August 2008 11:15] by Moderator

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