PostgreSQL for RedHat is an open source object-relational database system. An enterprise class database, PostgreSQL boasts sophisticated features such as Multi-Version Concurrency Control (MVCC), point in time recovery, table spaces, asynchronous replication, nested transactions (save points), online or hot backups, a sophisticated query planner or optimizer, and write ahead logging for fault tolerance. It supports international character sets, multi byte character encodings, Unicode, and it is locale-aware for sorting, case-sensitivity, and formatting. It is highly scalable both in the sheer quantity of data it can manage and in the number of concurrent users it can accommodate. There are active PostgreSQL systems in production environments that manage in excess of four terabytes of data.