MySQL™: The World’s Most Popular Open Source Database 185 The InnoDB Rollback Segment The History List: Committed Undo Logs m Undo Log Undo Log Undo Log Undo Log PURGE tes Free unnecessary y s log entries no tic Rollback segment as e used for: na g Crash recovery tr r pa Read isolation eth pe of ts r e slo da 00 A transaction e h 10 Undo Log: Updates, Deletes Two undo logs per trx eh T Undo Log: Inserts Discarded Copyright 2003 MySQL AB