Re: how to build a database from scratch

Sampo Syreeni wrote:
> On 2006-12-08, NENASHI, Tegiri wrote:
>
> >> 2PL does make life easy, but you can't use it unless you know precisely
> >> what data is going to be touched by a transaction when it begins.
> >
> > It is very strange what you say. Microsoft SQL Server utilizes 2PL
> > and I think DB2 also.
>
> I meant to say "ordered 2PL" or "2PL like that".

What is "ordered 2PL" ?

>The point was that 2PL
> alone does not guarantee deadlock-freeness.

Basic 2PL does not, but conservative 2PL does at some cost for sure.

> If you use it, at the very
> least you'll need to implement deadlock avoidance or recovery, and of
> course an efficient rollback mechanism.

All that is a sine non qua of anything that tries to call itself a database. How do you imagine a database without an undo or recovery mechanism ? Received on Fri Dec 08 2006 - 16:42:06 CET