What Is a Process Historian?
A process historian is a time-series database optimized for high-speed industrial process data. Unlike relational databases optimized for transactional operations, historians are designed to ingest thousands of tags at 1-second or faster rates, store data efficiently using compression algorithms tailored to process signals, and retrieve it rapidly for trend display, reporting, and analysis. Major commercial historians include OSIsoft PI System (now part of AVEVA), Honeywell Uniformance PHD, AspenTech InfoPlus.21, and Ignition Tag Historian from Inductive Automation. Open-source options include InfluxDB with Telegraf collectors and TimescaleDB for PostgreSQL-based deployments.