Assume two concurrent transactions: Tx 1 Tx 2
1. SELECT COUNT(*) FROM customers 2. DELETE FROM customers WHERE id=1 3. COMMIT 4. SELECT COUNT(*) FROM customers Let's assume that initially there are 3 records in customers with ids 1,2 and 3. For read-committed: Step (1) Returns 3. Step (4) Returns 2. For repeatable-read: Step (1) Returns 3. Step (4) Returns 3. There's a book called 'Principles of Transaction Processing' that will answer this and many more important TP subjects in detail. HTH, Juan Pablo Lorandi Chief Software Architect Code Foundry Ltd. [EMAIL PROTECTED] Barberstown, Straffan, Co. Kildare, Ireland. Tel: +353-1-6012050 Fax: +353-1-6012051 Mobile: +353-86-2157900 www.codefoundry.com > -----Original Message----- > From: A mailing list for Enterprise JavaBeans development > [mailto:[EMAIL PROTECTED]] On Behalf Of Milind Kulkarni > Sent: Monday, October 14, 2002 5:53 AM > To: [EMAIL PROTECTED] > Subject: Transaction Isolation Levels > > > Hi All, > > Can anyone explain me the difference between > transaction isolation > levels ' ReadCommitted' and 'RepeatableRead': > > It appears to be the same: > > ReadCommitted: Only data that have been committed by a > transaction can > be read by other transactions. > RepeatableRead: Only data that have been committed by a > transaction > can be read by other transactions, and multiple reads > will yield the > same result as long as the data have not been committed. > > Thanks, > Milind > > ============================================================== > ============= > To unsubscribe, send email to [EMAIL PROTECTED] and > include in the body of the message "signoff EJB-INTEREST". > For general help, send email to [EMAIL PROTECTED] and > include in the body of the message "help". > =========================================================================== To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff EJB-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".
