Ron Johnson wrote:
> Notes:
> a) this is, of course, not *sufficient* for multi-master
> b) yes, you need a fast, low latency network for the DLM chatter.
"Fast" is an understatement. The DLM you're talking about would (in our
case) need to use Spread's AGREED_MESS or SAFE_MESS service type,
meaning guarantee of total order. A transaction that needs any type of
lock sends that request into the DLM group and then waits. The incoming
stream of lock messages determines success or failure. With the overhead
of these service types I don't think one single communication group for
all database backends in the whole cluster guaranteeing total order will
be that efficient.
>
> This is a tried and true method of synchronization. DEC Rdb/VMS
> has been using it for 19 years as the underpinnings of it's cluster
> technology, and Oracle licensed it from them (well, really Compaq)
> for it's 9i RAC.
Are you sure they're using it that way?
Jan
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