Methods and systems for automatically tuning the undo retention in a database system are disclosed. The undo tablespace may be of a fixed size or may be set to be automatically extended. If the undo tablespace is of a fixed size, the undo retention is set to a “best possible” undo retention, which is calculated based on statistical data stored in the system. If the undo tablespace is configured to be automatically extensible, the undo retention may be set to be greater than the duration of the longest running query in the system. The duration of the longest running query may be calculated in a distributed process in which each instance broadcasts information about its longest running query to other instances.