ExDesc (extended descriptor)
- Last UpdatedJan 29, 2024
- 2 minute read
- PI System
- PI Interface for DNP3 3.3.1.38
- Interfaces
The ExDesc attribute configures a variety of run-time settings, two of which are included in every interface and are described in the following table.
Note: Keywords must be specified in upper case.
|
Keyword |
Description |
Example |
|---|---|---|
|
PERFORMANCE_POINT |
When set, such point stores the amount of time, in seconds, that it takes an interface to complete a scan for a particular scan class. The lower the scan time, the better the performance. |
PERFORMANCE_POINT For details, refer to the PI Universal Interface (UniInt) User Guide. |
|
TRIG or EVENT |
For event-driven input points: each time the specified point changes, the SQL query is executed. If the point name contains spaces, you must enclose it in single quotes. If there are subsequent parameters, you must specify a comma after the /EVENT specification. Valid conditions:
|
/EVENT=sinusoid, P… or /EVENT =sinusoid anychange, … |
Note: To assign values to replaceable parameters in SQL queries, you specify placeholders in the ExDesc attribute. Replaceable parameters in queries are indicated by question marks.
ExtendedDescriptor Length
Depending on the version of the PI API and the Data Archive, this interface supports an ExDesc attribute whose length is at most 80 or 1023 characters. The following table indicates the maximum length of this attribute for all the different combinations of PI API and Data Archive versions.
|
PI API |
PI Data Archive |
Maximum Length |
|---|---|---|
|
6.0.2 or later |
4.370.x or later |
1023 |
|
6.0.2 or later |
Earlier than 3.4.370.x |
80 |
|
Earlier than 1.6.0.2 |
4.370.x or later |
80 |
|
Earlier than 1.6.0.2 |
Earlier than 3.4.370.x |
80 |
Performance Points
For UniInt-based interfaces, the extended descriptor is checked for the string PERFORMANCE_POINT. If this character string is found, UniInt treats this point as a performance point.