Oracle backup using snapclone and container

[Sue Ellen Berkmeyer]

Hi,
Your help please.
Background:
Using snapclone for Oracle hot backups. I want to make absolutely sure I am getting a consistent backup of the production system for data integrity.
Process: Put the database in hot backup mode, take a snapclone to a container, take database out of hot backup mode.
The snapclone process takes about 20 minutes to complete in the background until it is "normalized".
Questions:
1) Does the snapclone copy the data from the time the database was in online backup mode or does it continue to copy data after the database is taken out of hot backup mode until it is fully normalized?
2) What is meant by normalization? I have found nil in the documentation.
Thank you,
Sue Ellen

[Víctor Cespón]

Hi, a snapclone is a point-in-time copy of the vdisk. Starts as a snapshot and copies all the content of the vdisk to the container.
Normalization is the process of completing the copy.
In new versions of the EVA firmware there is the possibility of making mirrorclones. This starts like a snapclone, but keeps being sincronized to the main vdisk until you stop the sincronization (fracture).
Then you perform backup and when finished, let the mirrorclone sincronize again. This way you only copy the modified data since the last backup, not the whole disk always.

[Orrin]

HI Sue,

For an absolutely consistent backup you have to do two things...

1. Make sure your Data and redo log volumes are on separate volumes.
2. Hot Backup.
3. Snap the data volume.
4. Rotate logs..
5. snap redo log volume.
6. Wait for Normalizing to complete.
7. Get database out of hot backup mode,
8. Backup the SNAP clones.

Hope this helps.

O

[Del_3]

Orrin, For us Oracle newbie types can you explain your steps? Why does the database and redo have to be on different volumes? I assume this does not necessarily mean seperate LUN's.

Also can you explain "rotate the logs"?

[Sheldon Smith]

I can't explain "rotate logs", but,
"different volumes" == "different vdisks" == "different LUNs".

[Sue Ellen Berkmeyer]

Thanks all for the replies.

It sounds like I should wait until the copy is finished or normalized and then take the database out of hot backup mode in order to ensure a consistent backup - that could be used for database recovery.

[Ted Buis]

Snapclones are usable immediately. You don't have to wait until the copy is completed. If you are going to discard the disk copy after the backup, why wait unit it is complete. DataProtector Zero Downtime Backup (DP ZDB) can automate this process for you. What is the OS on which you are running Oracle? Do you have a separate backup server to do the backup? What backup software are you planning to use? I am assuming your array is an EVA. DP ZDB works with either the XP or EVA arrays.

[Sue Ellen Berkmeyer]

I know snapclones are usable immediately for certain applications. However, for an Oracle hot backup, the datafiles need to be synchronized within the backup window. When the begin backup command is issued, the datafile headers are updated to the system change number (SCN). While in hot backup mode, the data blocks within the datafile can be read and updated. However, the datafile headers are not updated until the end backup command is issued. When datafiles are restored from a backup, all changes since the beginning SCN are rolled forward from the redo/archived logs. So in the case of the snapclone, I am concerned about copying data after the end backup command is issued. In which case, I will have an unusable backup.
To further answer your questions, the snapclone backups will be on a seven day retention on the EVA. The OS is Solaris. The UNIX SAs will use BakBone, Net Vault, to perform the SUN server and EVA nightly backups. I assume DP ZDB is a licensed product which is currently not in the budget.
Thanks for your input,
Sue Ellen