The article has a link to a previous blog post that expands on how Oracle does it (as well as other DB's). http://amitkapila16.blogspot.ca/2015/03/different-ap

The article has a link to a previous blog post that expands on how Oracle does it (as well as other DB's). http://amitkapila16.blogspot.ca/2015/03/different-approaches-for-mvcc-used-in.html http://amitkapila16.blogspot.ca/2015/03/different-approaches... > Oracle maintain old versions in rollback segments (also known as 'undo log').