Under Windows NT family operating systems the message is also written to the Application Event Log. The method used to do this has changed in 4.620, so that the event log also records which program encountered the error.
System error messages are produced if an error condition arises inside the DP4 libraries or interfaces while running a DP4 program. The text is taken from the SYSTEM mapset on the system database, or, from 4.620, the DP4 configuration file.
The message is written to SYSLOG.PRN, so that you can check the details of system errors at a later time.
Only the error numbers that are genuinely used as system errors are included in this information; other error numbers are associated with advisory or warning messages (displayed by sys_message() and sys_request()). sys_message() messages are merely advisory. sys_request() messages usually require the user to take some action to allow the program to continue to run. If the user chooses not to take the action the program will terminate cleanly. Messages associated with database contention errors may be used as either as system errors or as sys_request() messages, depending on the mode used by the program to access the database.
Programmers who want to handle system errors for themselves can assume that, unless otherwise noted, if the origin of a system error is classified as a program bug, it is possible to continue execution after the error. A better strategy is make sure that the error condition never arises by fixing the bug!.