Description: If the value of this variable is set to 1, the execution of the probe whose identifier takes the value given by the index will start. In GET operations, the value taken by this variable indicates the result of the last operation: ok (2), if the last operation was made succesfully; the value undefined (3) indicates that operations of this type have not been made yet. If the operation failed, this variable could take different values depending on the error cause: no-memory (4), if there was not enough memory to start the DNS probe; wrong-identifier(5) if the probe identifier introduced was not correct; already-started (6) indicates that the probe which was going to be started was started previously and is in execution; dns-uninitialized (7) if the DNS system has not been initialized; error (8) if another generic error has occurred.