RE: Locking

From: <Joel.Patterson_at_crowley.com>
Date: Thu, 17 Nov 2011 15:31:56 -0500
Message-ID: <C95D75DD2E01DD4D81124D104D317ACA1B8BB67F4E_at_JAXMSG01.crowley.com>



Also, there is an excellent discussion of this in Tom Kytes, expert oracle database architecture book. Topics include such things as comparing Transaction Isolation Levels between some DBMS's, locking, and concurrency.

A great book for developers, (and DBA's).

Transaction Isolation Levels -- Read uncommitted, read committed, repatable read, serializable, read only...

Joel Patterson
Database Administrator
904 727-2546

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Paul Harrison Sent: Thursday, November 17, 2011 2:53 PM To: oracle-l_at_freelists.org
Subject: Locking

Hi All,

Let's say I have 2 sessions open... session one updates a table and does not commit and can view the new updated data. session 2 is able to read the old data. How can session 2 read the old data if session 1 has an exclusive write lock on the table. Exclusive lock happens when updating a table?

Thanks,
Paul

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http://www.freelists.org/webpage/oracle-l Received on Thu Nov 17 2011 - 14:31:56 CST

Original text of this message