A program identifier, a limit identifier, a minimum value, and an increment value are stored to limit data. The limit identifier identifies a first variable used by the program. In response to storing a data value to a second variable, the stored limit identifier is found and a determination is made whether the stored limit identifier identifies the second variable. If the stored limit identifier identifies the second variable, a determination is made whether the data value is greater than the minimum value. If the data value is greater than the minimum value, the data value is stored to a log if an absolute value of the data value minus a most recently logged data value that was previously stored to the second variable is greater than the increment value. The execution of the program is halted or a user is notified in response to the storing to the log.