Thomas Kellerer wrote:

>
>>Does Oracle use MGA ? (I think it implements something like a log
>>for it, don't know how it could be considered MGA)
>
>
> I'm not sure what MGA stands for. My understanding is, that it's the
> same as Multiversion Concurrency Control. If that is true, then yes
> Oracle is using that.
>

Oracle's concurrency control is based on record locks, not record
versions. Postgres, Solid, InterBase, and Firebird use record versions
to determine whether two updates conflict. That's multiversion
concurrency control.

Oracle provides limited snapshots to support repeatable read without
maintaining read locks on records and access paths. So, Oracle has
multi-generational records - though I think I remember that they create
shadow pages rather than shadow records in the same page space as the
primary record. Claiming that as MGA seems strong since the
architecture is lock based and the multi-generational aspect is stuck on
as a bonus.

Regards,


Ann