Alarm history files (named for the alarm "Alarms.dat") contains a historical record of all alarm events that occurred in the system. VTS will automatically create this file in your application directory, even when there are no alarms used in the application. "Alarms.dat" contains the last 10,000 messages saved, and includes a record of all user-specified alarms, even if the module that generated the alarm event is no longer running.
Within the Alarm statement, you can specify for alarm messages to be placed in the "Alarms.dat" file. The file is constructed as any other VTS data logging file; it is generated with a Save statement, and may therefore be retrieved using a Get statement. As with all VTS historical data files, the time and date are recorded automatically with each entry. The data stored in this file, and the order in which it is stored is as follows:
1. Alarm event type – 1 byte;
2. Alarm level number – 1 byte;
3. Alarm category number – 1 byte; and
4. Alarm message – 80 characters of text.