All database users will recognize this situation. A user has started a query and it takes ages before the result set is available or, even worse, the database server seems unresponsive. In production systems, this is countered by logging all queries whose response time exceed a high-watermark or to tap into the system using a network monitoring system to observe its CPU and I/O behaviour. However, this only helps in post-mortem analysis. Monitoring all running queries alone is also not sufficient. It can only raise the red flag.