Re: Isolation level and Locks

From: Venkat <vreddy_at_ix.netcom.com>
Date: Fri, 24 Apr 1998 14:21:39 -0400
Message-ID: <6hql8v$4bn@sjx-ixn3.ix.netcom.com>

Yes, SQL Server does not have a concept of rollback segments - unlike in Oracle, writers block readers. In SS, you can't do a rollback unless you are in a transaction explicitly opened with BEGIN TRAN. If you execute an adhoc UPDATE or DELETE statement you can't rollback unless you replay the log and do a recovery to a time before the statements.

Venkat

>Am I right to say that Oracle uses Rollback segment to prevent a user to
>see uncommitted data vs SQL Server which uses Locks on those data ??
>
>To my mind, SQL Server has no Rollback segment and uses its log journal
>to rollback a transaction. To the opposite, Oracle uses rollback
>segments to undo a trnasaction without using the log journal (redo log)
>for an online session.
>What is the default isolation level for oracle ?
Received on Fri Apr 24 1998 - 13:21:39 CDT