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Re: RE: oracle or mssql

From: Tom Pall <tpall_at_realtime.net>
Date: Fri, 01 Nov 2002 08:59:47 -0800
Message-ID: <F001.004F9CEF.20021101085947@fatcity.com>


I work on contract and as a consulting Oracle DBA. I've migrated several companies from SQL Server because the block level locking did not scale to Oracle. I never had anyone ask me if I could convert them from Oracle to SQL Server.
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Thursday, October 31, 2002 11:19 AM

> Disagree.
>
> "row-level" locking in SQL Server was introduced in some capacity only in
> SQL Server 7 (not long time ago).
> Before, it was "block-level" locking, and I saw lots of problems with
that.
> It's not the length of the single statement (select/update/...) that
> matters. It's the length of the transaction, that causes a problem, if
> "block_level" locking is used (and could be automatically escalated to
> "extent" or even "table" level lock).
>
> Igor Neyman, OCP DBA
> ineyman_at_perceptron.com
>
>
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Thursday, October 31, 2002 10:18 AM
>
>
> > I don't see it as a gotcha, I've worked with SQL Server for almost 6
years
> > on some pretty big databases and have never had a problem.
> >
> > At the end of the day, locking is at the row level, locks are held for a
> > very short time (unless developers don't know what they are doing). A
read
> > will take a shared row level lock for a sub-second period of time
> > (potentially), if your update is blocked for 0.2 seconds are you going
to
> > notice ? You have to realise that with row level locking the scope for
> > blocking is minimal.
> >
> > Ade
> >
> > -----Original Message-----
> > Sent: 31 October 2002 14:04
> > To: Multiple recipients of list ORACLE-L
> >
> >
> >
> > But this default mssql behaviour is the performance 'gotcha' where
readers
> > block writers and writers block readers isn't it?
> >
> >
> > Mike.
> >
> > -----Original Message-----
> > Sent: 31 October 2002 09:12
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > 'Dirty reads' in SQL Server means that you can view records that have
not
> > been committed. This is implemented by setting the TRANSACTION ISOLATION
> > LEVEL to READ UNCOMMITTED.
> >
> > This is not default behaviour in SQL Server, the default TIL is READ
> > COMMITTED (for very good reason). I can think of very few situations
where
> > you would want to see uncommitted records.
> >
> > Dirty blocks in SQL Server/Oracle are the same thing ie. a block/page in
> > cache that has been changed but not flushed to disk.
> >
> > Ade
> >
> > -----Original Message-----
> > Sent: 30 October 2002 18:43
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > It sounds like he is saying that, once an "insert, update or delete"
> > statement has been issued (without a following commit), then the records
> > acted upon are now considered "dirty" - i.e. needing writing to disk.
> >
> > this is, of course, NOT what Oracle considers a dirty block.
> >
> > I agree with you, Jared!
> >
> > Tom Mercadante
> > Oracle Certified Professional
> >
> >
> > -----Original Message-----
> > Sent: Wednesday, October 30, 2002 1:21 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > At least one of us has the incorrect understanding of 'dirty' reads,
> > or I am taking you too literally, or something.
> >
> > What are you really saying?
> >
> > Oracle does not allow dirty reads.
> >
> > All queries are consistent to a point in time, the beginning
> > of a transaction, whether implicit (select) or explicit ( start
> > transaction ).
> >
> > SQL Server and Sybase do not guarantee this.
> >
> > The 'dirty' reads you are speaking of sound more to me
> > like sloppy programming.
> >
> > Is that what you're referring to?
> >
> > Jared
> >
> >
> >
> >
> >
> >
> > "Yechiel Adar" <adar76_at_inter.net.il>
> > Sent by: root_at_fatcity.com
> > 10/30/2002 08:54 AM
> > Please respond to ORACLE-L
> >
> >
> > To: Multiple recipients of list ORACLE-L
> <ORACLE-L_at_fatcity.com>
> > cc:
> > Subject: Re: RE: oracle or mssql
> >
> >
> > I would like to point out that what you call "dirty reads" are mostly
> > the correct reads. Oracle method IS the dirty read.
> >
> > I am sure that your users does at least 1000 commits to every rollback.
> > So when oracle gives you the data it already knows that this data is
> > wrong. If you do the query again a minute later you will get new results
> > that were available when you did the original query but were committed
> > later. So you get a 1000/1 chance to get incorrect data.
> >
> > The "dirty read" method, on the other hand, gives you the current
values,
> > believing that they will be committed in a moment. So you get 1/1000
> > chance
> > to get wrong data.
> >
> > Which odds will you bet on?
> >
> > Yechiel Adar
> > Mehish
> > ----- Original Message -----
> > To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > Sent: Tuesday, October 29, 2002 2:18 PM
> >
> >
> > List,
> > I'm always keen to refresh on database comparisons so thanks for
> > everyone's pointers.
> >
> > I'm surprised Oracle doesn't make more of an issue about their locking
and
> > concurrency methods (i.e. redo/rollback/undo).
> >
> > MSSQL seems to deal with it in two ways:
> > Default: readers and writers prevent writers from accessing data until
> > they
> > are finished with it!
> > Other method: no control, you just get dirty reads!
> >
> > Anyone got anything to add to this? Or am I wrong?
> >
> > - Mike.
> >
> >
> > -----Original Message-----
> > Sent: 24 October 2002 17:29
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > As I said, use mssql ONLY if your boss is willing to be strapped into a
> > MicroSlop only platform. If he's even remotely thinking of using a
> > different OS
> > then you can't use mssql.
> >
> > Dick Goulet
> >
> > ____________________Reply Separator____________________
> > Author: GKor_at_rdw.nl
> > Date: 10/23/2002 11:48 PM
> >
> > goodmorning
> > everybody who responded to my basic question : thanks
> >
> > summary
> >
> > professional : use oracle enterprise edition
> > semi professional : use oracle standard edition / mssql enterprise
edition
> > in all other cases mssql standard edition
> >
> >
> >
> > > -----Oorspronkelijk bericht-----
> > > Van: Mohammad Rafiq [SMTP:rafiq9857_at_hotmail.com]
> > > Verzonden: woensdag 23 oktober 2002 20:51
> > > Aan: Multiple recipients of list ORACLE-L
> > > Onderwerp: RE: oracle or mssql
> > >
> >
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > --
> > Author: Jenner Mike
> > INET: M.Jenner_at_southampton.gov.uk
> >
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> ==
> >
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > --
> > Author: Adrian Roe
> > INET: Adrian.Roe_at_telewest.co.uk
> >
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> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Igor Neyman
> INET: ineyman_at_perceptron.com
>
> Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> San Diego, California -- Mailing list and web hosting services
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Tom Pall
  INET: tpall_at_realtime.net

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
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Received on Fri Nov 01 2002 - 10:59:47 CST

Original text of this message

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