When the rule is triggered and its condition evaluates to true, the action of the rule must be executed. Possible actions in an MLS active database include,
- Data modification/retrieval operation – the action of the rule causes a data operation (insert, update, delete, access).
- Transaction operation – the action of the rule causes a transaction operation (e.g. abort).
- Application-defined operation – the action causes some procedure in an application to be executed.
- External operation – the action causes some external operations (e.g. informing the user).
Some active database languages allow a rule to specify multiple actions. Usually these actions are ordered which allows them to be executed sequentially.