[Veritas-ha] Oracle & DRL

[Doug Hughes]

On Tue, 3 Jun 2003, Andrey Dmitriev wrote:

> All,
>
> Can somebody point to an article/technote that discusses DRL, Oracle data
> files and redo logs.
>
> While I kind of understand what DRL is for, and how it might not be needed
> to recover volumes with datafiles, I don't understand how to make recovery
> of mirrors quicker.
>

DRL and oracle redo logs are for different purposes.
DRL is to make your mirrors resynch faster by logging what things
have been updated on which half (a redo-log of sorts at the vxvm
plex level).

DRL is discussed in the Veritas VxVM administration guide.

If you use VVR, you wouldn't necessarily need DRL because the
VVR logs make DRL somewhat redundant. Oracle logs act at a different
layer though. They protect the DB from partial operations that could
cause corruption during a crash.

host communications.
at the Ethernet hardware layer there's a MAC checksum, and TCP/IP
has a seperate checksum. They serve similar purposes for different
layers of the communication.
(The application may also contain even more checking)