Wikipedia has this to say about big data:
In information technology, big data[1] consists of datasets that grow so large that they become awkward to work with using on-hand database management tools. Difficulties include capture, storage,[2] search, sharing, analytics,[3] and visualizing. This trend continues because of the benefits of working with larger and larger datasets allowing analysts to "spot business trends, prevent diseases, combat crime."[4]
There are at least two main players: Hadoop and HPCC. Of note, many of the developers who created Clarion for Windows now work on HPCC.