"Dave Hau" <nospam_dave_nospam_123@nospam_netscape_nospam.net _nospam> wrote
in message news:SMvub.33830$sk4.10816@newssvr27.news.prodigy. com...
> "rkusenet" <rkusenet@sympatico.ca> wrote in message
> news:bpdm0b$1nhu6v$1@ID-75254.news.uni-berlin.de...
> >
> > "Daniel Morgan" <damorgan@x.washington.edu> wrote in message
> news:1069122434.507152@yasure...
> > > neo wrote:
> > >
> > > > Hi,
> > > > I have a problem to set a JDBC connection as READ UNCOMMITED.
> > > >
> > > > setTransactionIsolation(Connection.TRANSACTION_REA D_UNCOMMITTED)
> > > >
> > > > This is causing lots of blocking on tables
> > > > and update or insert doesn't work properly.
> > > >
> > > > Does anyone have any idea what I'm missing here?
> > > >
> > > > I asked i-net support and they suggested to call
> > > > setAutoCommit(false) after the above function
> > > > and it didn't work.
> > > > also suggested impltrans = true, and I changed that option on SQL
> > > > and it caused more blocking.
> > > >
> > > > Thanks in advance for any info.
> > >
> > > Why are you letting anyone, or any thing, read an uncommited
> > > transaction? If it is not committed ... it doesn't exist.
> >
> > ah.. this is a typical oracleisque response. Well there are
> > some circumstances when READ_UNCOMMITTED makes perfect sense.
> > For e.g. if u r running report on past data (like last week's report)
> > which is guaranteed to be read-only at the time of running
> > the report. why bother about COMMITTED data? a simple dirty
> > read will do the job as effectively, but more efficiently.
>
> Unless you're running low on memory and getting lock escalation from row
to
> page lock, I don't see why your past data (assuming you don't update past
> data) will have a lock on them. If there's no lock, then why would there
be
> a difference between doing READ_UNCOMMITTED and READ_COMMITTED on those
> rows. If there's no difference, then why did you say READ_UNCOMMITTED
will
> do the job "more efficiently"?

Never mind. I see - because of the overhead of the single read lock when
you use READ_COMMITTED. My bad.

- Dave


>
> Cheers,
> Dave
>
> >
> > Oracle's MVRC sounds great, but unless it gives an option
> > to bypass when it is unnecessary, it is an overkill.
> >
> > rk-
> >
> >
> >
>
>