I have a query that is ran by sp_executesql from within a 3rd party application. essentially it has a subquery within it. Often times this query will fill up the txn log since it is storing data in a temp table due to the sorting (I think). At any rate, until I either kill the spid, or the loop finally decides to end, this will often fill up the drive if goes unnoticed. When I run the execution plan I noticed Table Spool/Lazy Pool in the execution plan. But when I run the same query on a different server (that NEVER has this problem) I don't see the Table Spool Questions: What causes table spooling? is it a server setting or SQL setting that is different that I'm missing? why is it happening on one server and not the other? Thanks.