Logging the progress of software execution is a prophylactic measure designed to provide information on the causes of any software error which may occur. Certain information is stored in such a log continuously, i.e. even during normal (error-free) program execution. This information may take the form of memory addresses, the names of any modules which are used, program line numbers, etc. If an error occurs, it may be possible to localize it with the aid of the log. However, since this method results in the rapid accumulation of a large quantity of data (not all of which is necessarily useful for error analysis), it is sound practice to discard the data after a certain time. This can be done, for example, by overwriting the existing data cyclically, retaining only the last n entries in the log; in the event of an error, this is sufficient to ensure that the steps which led to the error are available for analysis.
The logging methods used in BS2000 are called error logging and tracing.