I had copied a script that contained a begin - end transaction clause to an update script. In the database it has to update two indicator fields on about 250,000 records. Now I first tested it on my development system with no issues. When I dropped it into production on a new instance of SQL it would take over 5 minutes and crash. The crash was because of out of disk space. It ran out of disk space because the tempdb grew to over 5GB. Now why would the exact same script on the exact same dataset grow to 5GB on one server while on another it did not grow at all. It stayed at 15MB.