There are a few show-stopping limitations and/or bugs to the PHD OLEDB provider (at the time of writing). The tables provided by the provider are:

PHD_DATA PHD_LINK_LIST PHD_PARENT_TAG PHD_RDI_LIST PHD_REDUCTIONS PHD_TAG PHD_TAG_BROWSE PHD_WRITE_DATA  

Anomaly One: Standard SQL cannot be used on all tables consistently

Some tables such as PHD_TAG can be queried successfully using a standard SELECT query against a linked server such as:

SELECT * FROM   your_linkedserver_name.standardapi.phd.phd_tag

This will return all your tags with relevant attributes such as their interpolation method, whether they have been manually inputted and their description.

However if you run a similar query against PHD_DATA (which holds the tag data such as the value, confidence, timestamps etc):

SELECT * FROM   your_linkedserver_name.standardapi.phd.phd_dataÂ

You get nothing.

If you specify a tag number and timestamp:

SELECT * FROM   your_linkedserver_name.standardapi.phd.phd_data...