In this post Luca Garulli tells his experience of using Terracotta as a distributed DBMS.
Since Terracotta assures high scalability and fail safe why don't use to store data in a distributed way? This is the reason why Luca Garulli wrote a small library to provide DBMS-like features on top of Terracorra.
Cool, but how about performance and high availability?
Read the post on his Blog and the flamed thread about Terracotta vs GigaSpaces.