Hi,
I am trying to understand how Oracle provides a guaranteed consistent
database backup when using the "split-mirror" online backup approach.
Because the "split-mirror" relies on the underlying hardware and/or
software to manage, it is outside of Oracle's influence, and in
particular, is relying on the Operating System to manage the
consistency of the data in the filesystems in the mirrors.
In AIX, there is no guarantee about data consistency (ie all blocks
written and metadata consistent) unless the filesystem is unmounted.
This is why it is recommended that a filesystem is unmounted when a
mirror split takes place, as it ensures that all data blocks are
written, and that no changes to data blocks are taking place as the
split occurs.
Hence, my question is how does Oracle (especially Oracle 8i which -
AFAIK - does not have I/O suspend and resume features) guarantee a
consistent and complete DB backup using the split-mirror online backup
approach, when the underlying filesystem may not contain all written
blocks if a split is taken with the filesystem mounted ?
I have read the Oracle Whitepapers on this backup approach, and still
cannot see how data integrity can be guaranteed for the data copy
residing in the mirror.
Ian Nash
Adv(Thanks)ance
Received on Thu Jan 31 2002 - 00:39:02 CST
