Supported Filter Attributes
The following table provides a list of attributes for which filtering is supported by the OPC Classic HDA server, and the corresponding ones in Historian, along with the supported operators for each.
| Historian Property Type | OPC Classic HDA server Attributes | Supported Operators |
|---|---|---|
| Data Type | OPCHDA_DATA_TYPE | OPC_HDA_EQUAL_TO |
| Tag Description | OPCHDA_DESCRIPTION | OPC_HDA_EQUAL_TO |
| Engineering Units | OPCHDA_ENG_UNITS | OPC_HDA_EQUAL_TO |
| Item ID | OPCHDA_ITEMID | OPC_HDA_EQUAL_TO |
Important: The OPC Classic HDA
server filter strings are
case-sensitive.
Although filtering is supported for the OPC_HDA_ARCHIVING attribute, do not use the
filtering in the OPC Classic HDA clients because the value of this attribute
is always true. Instead, you can refer to the log file to trace a
history of communication events dealt with by the OPC Classic HDA
server. You can also turn on the debug mode to more know more
details in the log file. If an invalid filter is passed by an OPC
HDA client, the OPC Classic HDA
server returns all the available
items in the address space.
Tip:
- The wildcard character (*) will return all the tags.
- The wildcard (key*) will return tags which begins with “key”.
- The wildcard (key) returns an exact tag name.