The alarm system for script applications is based upon four internal lists (numbered from 0 to 3), and a log file that records all alarm data, from events and alarm occurrences to acknowledgements (see Alarm Log Files (Alarms.log). The four internal lists are:
• The log (or history) list (index number 0);
• The active alarm list (index number 1);
• The unacknowledged alarm list (index number 2); and
• The current alarm list (index number 3).
You can decide whether or not each alarm will appear in any given list on an individual basis. It is good practice to avoid including alarms that are not in use in any list, since this will save time and memory during the execution of alarms.
When using alarm functions and statements, the list's index number can be used to select the list to be acted upon. These lists may be filtered to selectively ignore any combination of alarm events, namely: occurrence, clearing, acknowledge, enable, and disable. Filtering an alarm list allows great flexibility in the display of and actions upon alarms.
It is important to note that an alarm statement that occurs in a launched module will appear in the four alarm lists only so long as its module has not been stopped by a Slay statement. Once the Slay statement executes, all references to the alarm contained in that module will be deleted from all alarm lists.
The 4 alarm lists are described below.
The Log List - 0
The log list (index number 0) is a group of historical records containing the time, date, event, etc. for each existing alarm when it occurs, clears, or is acknowledged, enabled, or disabled. This list can contain up to 250 items and is maintained in memory (RAM) for fast updates. The log list contains information similar to that in the alarm history file ("Alarms.dat"); however, it will not save instances of an alarm activated from a module that is no longer running.
The Active List - 1
The Active list (index number 1) contains a list of all the alarms in the system that have occurred and are still active. The active list will grow and shrink as alarms occur and are cleared. There is no fixed upper limit on the length of the active list, but its maximum can never be greater than the total number of alarms defined in the system.
The Unacknowledged List - 2
The unacknowledged list is a list of all alarms that have occurred but have not yet been acknowledged. An alarm enters this list when it occurs. If the alarm clears before it is acknowledged, it will still remain in the list. If it then re-occurs before being acknowledged, it will not be re-entered in the list. There is no fixed limit upon the size of the unacknowledged alarm list but it can never be greater than the total number of alarms defined in the system.
The Current List - 3
The Current list is a combination of the active and unacknowledged lists. That is, it contains a list of all the alarms that are either active or unacknowledged. An alarm enters this list when it occurs and leaves it only when it has cleared and has been acknowledged. There is no fixed maximum length on the number of alarms in this list but it can never be greater than the total number of alarms defined in the system.
Using Combined Lists
Each list can be viewed in combined mode where only one entry in the list is used to record the start time and the end time for the alarm. This can save entries in the log list and result in a more compact list of alarms since the occurrence and clearing of the alarm appears on only one display line. Since only one log list entry need be used for the occurrence and clearing of the alarm, the limit of 250 entries in the list will allow a greater number of alarm history events to be viewed from RAM. Combined mode does not affect the unacknowledged alarm list or the Alarms.DAT file.
Significance of Colors in the Alarm Lists
The color of a line of text in an alarm list denotes the current status of the alarm, as follows:
• Red Occurrence of an alarm
• Yellow Alarm has been acknowledged
• Green Alarm has cleared
• Cyan Enabling/disabling of an alarm
The section that follows provides information on the alarm history file (Alarms.dat).