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Re: How to make lock escalation look good...

From: Andy <andy.spaven_at_eps-hq.co.uk>
Date: Wed, 21 May 2003 10:37:25 +0100
Message-ID: <FJHya.199$95.40@newsr2.u-net.net>


Nuno

I especially like the absence of pieces of information or disingenous white lies.

1 - no mention is made of what happens should the process trying to escalate exclusive locks to an exclusive table lock find that other processes currently have row locks on rows in that table. This task that "can therefore finish its work and get out of everyone elses way" must surely have to wait for those locks to be released (here I'm talking about exclusive locks not read locks) and therefore not "get out of everyone elses way".

2 - the implication that Oracle is storing locking information to disk whereas IBM use memory - the implication that this is faster. Given that any block currently being amended will be in the block buffer cache - the locking information will actually be added at this point in time - i.e. in memory.

3 - the implication that Oracle is wasteful in using more disk space - up to 12% according to the document - has anyone ever seen an ITL of 4 or more even on an intensive OLTP app. I guess there must be some but I've not yet witnessed one. Anyone know of sites still using 2K block size for new deployments for OLTP with Oracle ? That aside has anyone had a customer deploying a multi-terrabyte storage system even seriously consider trying to save a few % of space and therefore a few % on disk costs by switching database vendors.

Does anyone on this NG have experience of systems using page locking and lock escalation (I know there must but does anyone have any comments to make) especially on DB2 ? I'd be interested to learn more.

It's the sort of disinformation seen in this doc that drives me crazy because it's just this sort of "information" that a sales & customer account managers will give to some non technical manager tasked with purchasing a new system. I hate it because I then end up explaining to people why such and such an official document isn't quite so relevant / appropriate or is in some cases not even true.

Oracle are just as bad. I'd love to see a DB2 specialist take the Oracle document mentioned at the foot of the IBM one to pieces with "inaccuracies". I'm sure there are some - it's marketing literature by another name as Daniel points out.

Andy

"Nuno Souto" <wizofoz2k_at_yahoo.com.au> wrote in message news:73e20c6c.0305201424.4b707c41_at_posting.google.com...
> Just came across this pearl at an IBM site:
>
> http://www-3.ibm.com/software/data/pubs/papers/locking/locking.pdf
>
> Amazing! How to make lock escalation "look and feel" like
> an "advantage", while completely distorting and misrepresenting
> the Oracle lock mechanism.
> <sigh>
>
>
> Cheers
> Nuno Souto
> wizofoz2k_at_yahoo.com.au.nospam
Received on Wed May 21 2003 - 04:37:25 CDT

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