Google Isolation Level. Basically the default is

READ COMMITTED.

That means if it is executing an UPDATE, DELETE or INSERT (or SELECT INTO etc) on a table you attempt to query at the same time, the query needs to wait until all the transactions are committed before being executed (called a read lock). All subsequent read queries will queue behind that one, which of course can escalate to extent, page or even table locks.

That is important for some applications where accurate data is critical. If an application is making an update to a table you don't want to view the new data until the transaction has completed successfully. However, with the Wrath it doesn't matter since the posting method is just fire and forget.

If you SET TRANSACTION_ISOLATION_LEVEL READ UNCOMMITTED (or whatever the MySQL syntax is - I am more a SQL Server man myself) then your queries will simply query the data in the tables whether it is committed or not.

This means that if you are manipulating data in a table and querying it at the same time, the read queries will not wait for any transactions to commit so you get NO locks at all, avoiding escalating row level locks as well.

Then do a smell up the USB.

Innit.

Posted By: Steve in Holland, May 9, 16:21:50