RMAN and RAC databases backup

[patrick196901]

Hi Tim,

I an writing you today as I need the answer of an Oracle expert before making a huge mistake.

We have a two nodes RAC cluster running on Solaris 10, and we are going to migrate it from Oracle 10g R2 to 11g R2 on Solaris 11. We have required the help of an external consultant to help us in this migration. My question is about the RMAN recovery catalog linked to RAC instances. The consultant asked us to create two recovery catalogs, on two different servers (virtual machines), and on each site, each of them backing up one node of the cluster.

For instance imagine site A and B. We have one node of our RAC cluster running on site A and the other one on site B. I was thinking to create one RMAN catalog in a database hosted on a virtual machine on site A, and it would backup one node of our RAC, either instance on node A or B. But the consultant told us in case of site A becomes unavailable and if unfortunately we have to perform a restore/recovery of one instance in node B then as the recovery catalog is on site A it wouldn't be available and so impossible to perform the restore/recovery. So to avoid this situation he advised us to create two RMAN recovery catalogs, one on each node, and each RMAN recovery catalog would backup each instances on each nodes of our RAC. So if we have a database named DB1, one instance of site A named DB1_A, and the other instance on node B named DB1_B. Then recovery catalog on site A would backup instance DB1_A, and recovery catalog on site B would backup instance DB1_B.

What do you think of that? Is that pertinent or not at all?

Thanks in advance for your answer.

Regards

Patrick

[Tim...]

Hi.

So as I understand it your RAC installation is a stretch cluster between two sites. In this case it makes sense to consider a recovery catalog in each location because the loss of one site will serious affect you if that site also contains the recovery catalog etc.

How do you maintain two recovery catalogs? There are several alternative including:

1) Backup separately in both sites.
2) Backup in one site. Transfer the backups to the second site and transfer a copy of the catalog.

Personally, I think running two separate backups of one database is a bit over the top. Especially if it gets rather big. That seems like an unnecessary overhead to me. With a RAC installation, there is only one database, so why back it up multiple times?

Personally I would pick option 2 and transfer the backups over to site 2, so you have copies of the backups in both locations, then do a regular transfer of the recovery catalog over to the second site. This could be as simple as an export from site A and an import to site B. It should be easy to script.

I guess my question would be to ask the consultant what benefits (s)he sees in doing two backups compare to 1 and a transfer. It may be the network transfer is more of a consideration than the overhead of the second backup etc. I would need to know the logic of the decision process to know if I agree with them or not.

Cheers

Tim...

[patrick196901]

Hi Tim,

Thanks for your help. I will apply what you wrote in your answer.

Regards

Patrick

[Tim...]