Sources familiar with Defence's operations, who requested anonymity, told Computerworld the department is using the MySQL relational database system for a "large-scale application".

Exact details of the MySQL implementation at Defence remain scant, but the source did say the amount of data managed could be as high as "many terabytes".

Often seen as the last bastion of commercial software, open source databases have slowly progressed from running Web-tier and other edge applications to central business and transaction processing systems.

In August, Computerworld reported that Sydney-based financial services firm MoneySwitch developed a transaction processing system with MySQL as the database, making it a critical part of its infrastructure.

Local MySQL users also include Service Central, Soul, WIN Television, De Bortoli Wines, SBS Television, Aviva Group, and Auspost.