Understanding PI Server ARC and ANN Files: What You Need to Know

If you’re new to OSIsoft PI System, you might come across file types like .ARC (archive) and .ANN (annotation) files and wonder what they are or how to use them with your PI Server. This post will guide you through what these files are, what you can do with them, and important considerations for importing or working with PI archived data.

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What Are ARC and ANN Files?

• ARC files: These are PI Server archive files. They store the compressed, time-series data that the PI Data Archive collects from connected sources.
• ANN files: Each ARC file may be accompanied by an ANN (annotation) file, which stores annotations related to events in the archive, such as manual comments or data flags.

These files are fundamental to the way PI Server stores and manages historical data.

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Can You Import Archived Data with ARC/ANN Files Alone?

The short answer is: not usually. While ARC and ANN files contain your historical data and its annotations, they reference PI Points (tags) by unique internal IDs, not by user-friendly tag names. To interpret and reuse archived data, you also need:

• PI Points Database (PIPoints.dat): This file maps internal IDs to PI Point names, types, and configurations. Without the corresponding PI Points database, the data in ARC/ANN files is unintelligible to the PI Server.

Key Takeaway: You need both the archive (ARC), annotation (ANN), and the PI Points (PIPoints.dat) files from the same system to successfully move or reconstruct an archive.

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Steps to Use ARC/ANN Data on Another PI Server

1. Get All Required Files: Obtain the matching ARC, ANN, and PIPoints.dat files from your source.
2. Backup Your Server: Before making any changes, always perform a backup of your existing PI Server data and configuration.
3. Stop the PI Data Archive: Pause the PI Server to avoid data corruption during the file transfer.
4. Place Files in Appropriate Locations: Copy the ARC and ANN files to your PI archive data directory, and the PIPoints.dat file into the appropriate directory.
5. Start the Server and Reprocess Archives: Once files are in place, start the server. You may need to reprocess or recalculate the archives (using system management tools).

Note: Be aware that mismatched versions, differing point configurations, or discrepancies between files could cause import errors or data corruption.

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Training and Best Practices

Working with the PI Data Archive and handling archive files can be complex, especially when importing or restoring data. OSIsoft recommends:

• Taking Formal Training: Courses like “PI System Manager I: Essential Skills” provide a strong foundation in managing and maintaining the PI Server, its data archives, and configuration.
• Using Official Documentation and Forums: Refer to PI System documentation and community forums (e.g., vCampus) for sample data, troubleshooting, and best practices.
• Engage with the Discussion Threads: If you need to populate your PI Server with sample or arbitrary data, check out community discussion threads for scripts, tools, and workflows.

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Conclusion

While ARC and ANN files are essential pieces of your PI Server’s data history, they are only usable if you have the corresponding PI Points database. For anyone managing PI systems—or developers interested in data integration—proper training and an understanding of archival structures are crucial.

If you’re in the early stages, consider OSIsoft’s training modules, and don’t hesitate to engage with the PI System user community for further guidance.

Useful Links:

• PI System Manager I: Essential Skills Training
• PI System Online Community
• Official Documentation