1. An apparatus for monitoring execution plans of a relational database, the apparatus comprising: a) at least one of a volatile and a non-volatile memory; configured to store a detector agent and an alert agent; and b) a microprocessor operative to: i) execute code of the detector agent to monitor the performance of the relational database to detect an execution plan change for at least one database statement handled by the relational database; and ii) execute code of the alert agent to generate an alert signal, contingent on results of said detecting of said execution plan change.