A method and apparatus for storing snapshots (pre-modification copies of data) in short term memory is disclosed. In an embodiment, if short term storage is clogged, snapshot chains are copied to longer term memory. In an embodiment, snapshot chains that are older than any active transaction are discarded,...http://www.google.com.au/patents/US20060036655?utm_source=gb-gplus-sharePatent US20060036655 - Storage of multiple pre-modification short duration copies of database information in short term memory
