Understanding How ClearSCADA Applies Alarm Filters to Embedded Alarms Lists

Whether you define the Alarm Filter String manually, or allow ClearSCADA to create the string based on your selections on the Filter window, you need to understand how ClearSCADA applies alarm filter strings. In this section, we explain how the alarm filter strings of User accounts and Alarms Lists are used and describe how ClearSCADA determines which filter settings take precedence.

Once you understand how ClearSCADA uses Alarm Filter Strings, you will be able to create your own alarm filters without experiencing unexpected results.

In ClearSCADA, both User accounts and Alarms Lists (including embedded Alarms Lists) have Alarm Filter String settings. These settings define the filter settings that are applied to an Alarms List when it is first displayed.

A User account’s Alarm Filter String is defined on the User Form and it is applied automatically whenever that user accesses an Alarms List. However, ClearSCADA only applies the clauses if they do not conflict with the clauses in the list’s own Alarm Filter String.

Alarms Lists also have an Alarm Filter String that is applied whenever the lists are displayed. Any settings that are explicitly defined in the filter string for an Alarms List take precedence over the settings defined in any User alarm filter string.

When an embedded Alarms List is displayed, ClearSCADA merges the filter string defined for the Alarms List with the filter string defined for the current user’s User account. It then applies the resulting string to the embedded Alarms List.

If the filter string for the User account does not conflict with the filter string for the embedded Alarms List, ClearSCADA can merge the strings and apply both filters simultaneously. However, if there is a conflict, ClearSCADA will use the filter values in the embedded Alarms List’s filter string in preference to those defined for the User account’s filter string (on a clause-by-clause basis). This means that the embedded Alarms List’s filter string takes precedence over a User account’s alarm filter string.

However, there is one situation in which the User filter string takes precedence over the embedded Alarm’s List’s filter setting—when the default filter values are in place but not specified in the string for the Alarms List. For more information on this special case, see Making an Embedded Alarms List’s Default Filter Settings Take Precedence.

Now that you have an appreciation of how ClearSCADA uses the Alarm Filter String settings, you can make an informed decision:

If you want to apply a filter that differs from the default filter values, you can choose to:

• Enter the alarm filter string manually (see Define an Alarm Filter String for an Embedded Alarms List Manually). You will need an understanding of the required syntax: see Alarm Filter String Syntax in the ClearSCADA Guide to Alarms.

or

• Use the Filter window to choose the filter settings. ClearSCADA will then generate the appropriate filter string for you (see Use the Filter Window to Create an Alarm Filter String for an Embedded Alarms List).
  

If you want to use the default filter values for the embedded Alarms List and are willing to let User account filter strings take precedence:

• Leave the Alarm Filter String for the List blank (see Define an Alarm Filter String for an Embedded Alarms List Manually).

or:

• If the default filter settings are not currently in place, you can use the Filter window to reset the various options to their default value (see Use the Filter Window to Create an Alarm Filter String for an Embedded Alarms List).
  

If you want to use the default filter values for the embedded Alarms List and you want these default values to take precedence over any User account filter strings:

• see Making an Embedded Alarms List’s Default Filter Settings Take Precedence.