Patent ID: 7437525

Claim:
A computer-implemented method of retaining undo information, comprising: storing data that indicates whether or not undo records have guaranteed undo retention, wherein the undo records include a first subset of undo records that have guaranteed undo retention and a second subset of undo records that do not have guaranteed undo retention; wherein each undo record of the second subset of undo records can be overwritten before an expiration time associated with said each undo record has elapsed; determining that there is new undo information to be stored; wherein the undo information indicates undo operations which, when performed, reverse changes made to data; determining whether there are any usable undo storage spaces; if there is a usable undo storage space, then storing the new undo information to the usable undo storage space; and if there is no usable undo storage space and if there is a particular undo storage space storing one or more undo records, from a set of undo records, that do not have guaranteed undo retention, then storing the new undo information to the particular undo storage space.