Re: Upgrade issue (again).

On Thu, May 17, 2001 at 12:43:49PM -0400, Rod Taylor wrote:
> Best way to upgrade might bee to do something as simple as get the
> master to master replication working.

Master-to-master replication is not simple, and (fortunately) isn't
strictly necessary. The minimal sequence is,

1. Start a backup and a redo log at the same time.
2. Start the new database and read the backup.
3. Get the new database consuming the redo logs.
4. When the new database catches up, make it a hot failover for the old.
5. Turn off the old database and fail over.

The nice thing about this approach is that all the parts used are
essential parts of an enterprise database anyway, regardless of their
usefulness in upgrading.

Master-to-master replication is nice for load balancing, but not
necessary for failover. Its chief benefit, there, is that you wouldn't
need to abort the uncompleted transactions on the old database when
you make the switch. But master-to-master replication is *hard* to
make work, and intrusive besides.

Nathan Myers
ncm(at)zembu(dot)com