1. A method for managing a plurality of computing machines, the method comprising: deploying an indication of a management activity having an applicability rule to selected one or more of the computing machines to cause each of the selected computing machines fulfilling the applicability rule to execute the management activity on the selected computing machine, receiving an error message for each failure computing machine of the selected computing machines wherein the execution of the management activity has failed, determining at least one relevant property of each failure computing machine among a plurality of selected properties of the computing machines according to the corresponding error message, collecting a value of at least part of the selected properties for at least part of the computing machines, the values of the selected properties comprising a failure value of each relevant property for each failure computing machine, and updating the applicability rule according to the failure values.