Never use DTA against a production database, it's incredibly dangerous. It's testing workloads so it will put a lot of load on whatever server it's pointing at. If you have to use it at all, take a trace from production and run it against a test server, get it to recommend only, not implement anything and test every single recommendation it makes as most will be unnecessary.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability