Sure it does. Changing the transaction isolation level affects how data is read from the database. TRANSACTION_READ_COMMITTED waits for a read lock before reading data and ensures that the data being read is in a consistent state. Lower isolation levels may allow data to be read that's inconsistent -- data from a transaction that hasn't been committed, yet, and therefore may be rolled back. However, that doesn't mean lower isolation levels are "bad". They can relieve a lot of locking contention on the database when used with queries that don't need perfectly consistent data. It just depends on how critical the info you're pulling with this particular query is.
For example: are you tallying the number of visitors to your website or are you doing financial transactions? With the former, reading "dirty" data may not matter that much. With the latter, it may be critical that you have consistent data. If your data's not that critical, you may get a lot of benefit from lowering your transaction isolation level. Thanks, --jeff ----- Original Message ----- From: "David Frankson" <[EMAIL PROTECTED]> To: "Tomcat Users List" <[EMAIL PROTECTED]> Sent: Monday, November 19, 2001 11:42 AM Subject: Re: AW: Java program interferring with Tomcat > > Not with SQL Server. If thread A has a write lock on a table, thread b > will > > wait until the write is completed before reading. If thread A is in a > > transaction that is long running then a perfectly funcitoning application > > can seem to hang. Its also possible that some form of infinite loop or > > deadlock in thread A could cause it to never release the transaction, > making > > you either kill the application or use Enterprise Manager to kill the > lock. > > Does changing the transaction isolation level affect things? The tomcat > application is a high traffic transactional system, and the commandline app > is a read-only data export tool that fires off twice a day. Both are set to > TRANSACTION_READ_COMMITTED. > > Dave > > > > > -- > To unsubscribe: <mailto:[EMAIL PROTECTED]> > For additional commands: <mailto:[EMAIL PROTECTED]> > Troubles with the list: <mailto:[EMAIL PROTECTED]> > -- To unsubscribe: <mailto:[EMAIL PROTECTED]> For additional commands: <mailto:[EMAIL PROTECTED]> Troubles with the list: <mailto:[EMAIL PROTECTED]>
