If the database system you are monitoring is for decision support (DSS), and the queries are long and complicated, don't have the quality control (QC) agent run a large query.

For example, if your database is used for transaction processing and heavy decision-support (DSS) queries, you can be sure that a non-scheduled DSS query will trash your transaction performance.

General tuning tips are the same regardless of the database workload, but differences do exist between OLTP and DSS workloads.