RE: Is it possible to use nolock type of hint in query

  • From: "Norman Dunbar" <norman.dunbar@xxxxxxxxxxxxxxxxxxxxxxxxx>
  • To: <paul.baumgartel@xxxxxxxxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>, <ineyman@xxxxxxxxxxxxxx>
  • Date: Mon, 14 Aug 2006 10:44:41 +0100

Morning all,

> "Igor Neyman" <ineyman@xxxxxxxxxxxxxx> 08/11/06 08:50pm >>>
> Shouldn't SELECT... FOR UPDATE be used in this case (and not "dirty"
> reads)?


Am I the only DBA in the entire world who disagrees with the use of

To me, this statement is a sure sign of 'lazy developer syndrome' - and
having been a developer, don't think I'm having a go at developers in
general. (Well, Java developers deserve everything they get, but the
rest are ok <GD&R>)

What's wrong with writing correct 'error' handling to get around the
fact that some other session has updated your data in the time between
your session reading it and then trying to write back the amendments ?

Dave Ensor's book about Oracle Design has a good chapter on this very
subject, which basically boils down to 'lock late and lock for a short
time only'. SELECT ... FOR UPDATE is a 'lock early and lock for as long
as possible' technique.

The number of problems I have to deal with in applications I have
supported (and support) which have enqueue problems caused by this very
statement is a nightmare. I'm afraid that even Oracle are causing me
grief at the moment - in Spatial systems, they have fixed a bug by
adding FOR UPDATE to the end of a select from
MDSYS.SDO_INDEX_METATDATA_TABLE - unfortunately, one of our systems (web
based, Java code, etc etc) takes longer than zero time to do its
transaction(s) and locks out other users.



Norman Dunbar.
Contract Oracle DBA.
Rivers House, Leeds.

Internal : 7 28 2051
External : 0113 231 2051

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