Method and apparatus for incremental undo

A computer-readable medium carrying one or more sequences of instructions for performing incremental undo when recovering a computer database from a failure, wherein execution of the one or more sequences of instructions by one or more processors causes the one or more processors to perform the steps of:

• storing changes for a plurality of data blocks in a single undo record;
• establishing as a current rollback entry, a rollback entry that belongs to a plurality of rollback entries within said single undo record, said plurality of rollback entries corresponding to a particular data block in said plurality of data blocks;
• examining a status flag corresponding to said current rollback entry to determine whether said current rollback entry has been applied;
• establishing a next rollback entry in said plurality of rollback entries as said current rollback entry without applying said current rollback entry when said current rollback entry has been applied;
• and
• when said current rollback entry has not been applied, then:
• retrieving said current rollback entry from said plurality of rollback entries;
• applying one or more changes indicated by said current rollback entry to said particular data block;
• and
• setting said status flag in said undo record to indicate said current rollback entry has been applied.

A computer system comprising a database server, wherein said database server is configured to recover a particular data block from a failure by performing the steps of:

• storing changes for a plurality of data blocks in a single undo record, said plurality of data blocks including said particular data block;
• establishing as a current rollback entry, a rollback entry that belongs to a plurality of rollback entries within said single undo record, said plurality of rollback entries corresponding to said particular data block;
• examining a status flag corresponding to said current rollback entry to determine whether said current rollback entry has been applied;
• establishing a next rollback entry in said plurality of rollback entries as said current rollback entry without applying said current rollback entry when said current rollback entry has been applied;
• and
• when said current rollback entry has not been applied, then:
• retrieving said current rollback entry from said plurality of rollback entries;
• applying one or more changes indicated by said current rollback entry to said particular data block;
• and
• setting said status flag in said undo record to indicate said current rollback entry has been applied.