Query on hot backup

[eric73]

Hi All,

I have a question on hot backup.

I understand that the database need to be in archivelog mode before we can start any online backup.

But I'm confused about how Oracle handles changes to the datafiles during online backup mode.

Does Oracle continue to write changes to the datafiles during backup mode?
Does Oracle continue to archive online redo logfiles to archived logfiles? or is this process frozen during backup mode?

Appreciate any input.

Thanks
Eric

[malay_biswal]

No It keeps track of the Changes made and those are stored in archive log.

[eric73]

Hi,

So if you say that Oracle do not write changes to the datafiles, and is stored in the archived logfiles... then what happens when some transactions are still happening during the backup mode period?

Well, let's say if there is an insert or update operation going on during backup mode, and these changes are not written to the datafiles but are stored in the archived logfiles, then when the database is out of backup mode, how will the changes in data be written or sync to the datafiles without applying the archived logfiles?

Thanks
Eric

[pando]

yes data are still written during hot backup otherwise you need an infinite buffer cache

archived logs are generated as well

[dbtoo]

http://www.dizwell.com/prod/node/10

[BV1963]

This topic is so beat to death. Oracle writes both commited and not commited transactions (dirty buffers) to the datafiles on the event which is called a checkpoint.

[eric73]

http://www.dizwell.com/prod/node/10

Thanks for all you help.
Finally clear up my understanding on archiving in backup mode.

Howard's explanation is spot on and easier to digest.

Cheers
Eric