Finding Data Metacat

Introduction

Modern Mu2e data handling stack:

• metacat: File catalog database and query tool
• Rucio: File location catalog and data movement service
• mdh: Mu2e convenience scripts wrapping metacat and Rucio
• dCache: Distributed storage (tape/persistent/scratch)

Authentication:

• Generally automatic if you have a Kerberos ticket
• Run mu2einit to get credentials

Dataset Monitor:

• View all datasets and status: https://mu2e.fnal.gov/atwork/computing/ops/datasetMon.html

Files and Datasets

Registered vs Unregistered Files

Registered files:

• Cataloged in metacat database
• Must follow naming conventions
• Located in standard dCache directories
• Subject to collaboration policies
• Can be owned by collaboration (mu2e) or user (your username)

Unregistered files:

• For local/temporary use
• Not in catalog
• No naming restrictions
• Your scratch area: /pnfs/mu2e/scratch/users/$USER

File Naming Convention

All registered files must follow the six-field pattern:

tier.owner.description.config.sequencer.format

Example:

sim.MyUsername.dh_tutorial.2026-02-12.001000_000001.art

Fields:

• tier: Data processing level (sim, dig, mcs, nts, etc.)
• owner: mu2e (collaboration) or your username
• description: Brief descriptor for this file type
• config: Configuration identifier or date
• sequencer: Run/subrun number (unique per file)
• format: File format (art, root, tar, tbz, fcl)

Dataset Names

Dataset = file name without the sequencer field:

tier.owner.description.config.format

Example:

sim.MyUsername.dh_tutorial.2026-02-12.art

All files in a dataset are considered "more of the same."

Namespaces and Data Identifiers (DIDs)

Namespace = owner prefix: