pi server which database using internally is sql server for keeping data [archive]?
The PI Data Archive internally does not use a SQL (relational) database to store the time series data. It uses a proprietary storage mechanism. The AF part of the PI System does use SQL.
Are you running into any issues, or were you just curious ?
Just to add a little to Dan's answer, PI AF stores it's data in a SQL database. That being said, customers should treat the PI AF SQL database as a black box, meaning that it shouldn't be interacted with directly.
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