It is important to remember that the time limit generated by the optimizer is only an estimate. The actual query runtime could be more or less than the estimate, but the value of the two should be about the same. When setting the time limit for the entire system, it is usually best to set the limit to the maximum allowable time that any query should be allowed to run. By setting the limit too low you will run the risk of preventing some queries from completing and thus preventing the application from successfully finishing. There are many functions that use the query component to internally perform query requests. These requests will also be compared to the user-defined time limit.