Thanks. Its an issue when every database vendor does it wildly different.. sigh...I haven't been using MSSQL a long time. I like it.. but sometimes I dont :)
On Tue, Dec 2, 2008 at 10:58 AM, Paul Heinz <[EMAIL PROTECTED]> wrote: > Kyley wrote: > > > I thought Snapshot isolation is best for > > reporting with concurrent data.. Hmm in interbase it versions > > off data without locking other transactions.. does MSSQL just block? > > In versions prior to SQL Server 2005, yes. It used to just block writes > to any unread row until it had been streamed to the requesting client. > So, readers blocked writers and writers blocked readers. The worst of > both worlds. > > With SQL 2005, they implemented a solution similar to Oracles rollback > segments to support snapshot read isolation without blocking writes. In > fact, SQL 2005 specifically addressed the prime concern that stopped > sites migrating away from Oracle. Funny that :-) > > It's still not as 'nice' an implementation as > Firebird/Interbase/Postgresql (i.e. proper MVCC). Oracle can exhaust > it's rollback segments (the dreaded ORA-01555) and SQL Server can run > out of TempDB space. This usually occurs in the face of long running > reporting transactions against a database facing high insertion or > mutation rates. In these cases, both Oracle and SQL Server abort the > reporting transaction which is rather 'unhelpful' but given their > implementation, they have no other option. > > Anyway, to avoid reference to prayer and to understand more of how this > all works internally I recommend the late Jim Gray's book 'Transaction > Processing: Concepts and Techniques'. It's pretty much the Bible for > transaction processing IMO. It was invaluable when I was implementing > client-side transaction processing in the Accredo database engine. > > TTFN, > Paul. > > > > > _______________________________________________ > NZ Borland Developers Group - Delphi mailing list > Post: delphi@delphi.org.nz > Admin: http://delphi.org.nz/mailman/listinfo/delphi > Unsubscribe: send an email to [EMAIL PROTECTED] with Subject: > unsubscribe > -- Kyley Harris Harris Software +64-21-671-821
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