Learn about input processing: updating PI tags from an RDBMS

To update PI tags with values retrieved from the RDBMS, you define a SELECT query or stored procedure that returns result rows from the RDBMS, and, if necessary, configure the target tags that are to be updated with the data returned by the query.

When you update tags, you write a value, timestamp and status (and, optionally, the questionable flag and annotations). You can configure updates as either scan- or event-based. Scan-based updates occur when the tag is scanned, while event-based updates are triggered by changes to a point referenced by the /EVENT or /TRIG keywords.

When data is written to a tag, the tag stores a value only if the status is good. If the status is anything other than good, only the status is stored.