(University of Glasgow/CERN)
The ATLAS TAG database is a multi-terabyte event-level metadata selection system,
intended to allow discovery, selection of and navigation to events of interest to an
analysis. The TAG database encompasses file- and relational-database-resident
event-level metadata, distributed across all ATLAS Tiers.
An oracle hosted global TAG relational database, containing all ATLAS events,
implemented in Oracle, will exist at Tier 0. Implementing a system that is both
performant and manageable at this scale is a challenge.
A 1 TB relational Tag database has been deployed at Tier 0 using simulated tag data.
The database contains one billion events, each described by two hundred event
metadata attributes, and is currently undergoing extensive testing in terms of
queries, population and manageability. These 1 TB tests aim to demonstrate and
optimise the performance and scalability of an Oracle TAG database on a global scale.
Partitioning and indexing strategies are crucial to well-performing queries and
manageability of the database and have implications for database population and
distribution, so these are investigated. Physics query patterns are anticipated, but
a crucial feature of the system must be to support a broad range of queries across
Concurrently, event tags from ATLAS Computing System Commissioning distributed
simulations are accumulated in an Oracle-hosted database at CERN, providing an
event-level selection service valuable for user experience and gathering information
about physics query patterns.
In this paper we describe the status of the Global TAG relational database
scalability work and highlight areas of future direction.
An oracle hosted global TAG relational database prototype, deployed at cern as part
of multi-terabyte event-level metadata selection system, is discussed.
This is an ATLAS Offline Computing abstract, Distributed data analysis and
information management track assigned by the ATLAS speakers committee.