Mode 1 – Doesn’t crash MySQL when it sees a corrupt page
Mode 2 – Doesn’t run background operations
Mode 3 – Doesn’t attempt to roll back transactions
Mode 4 – Doesn’t calculate stats or apply stored/buffered changes
Mode 5 – Doesn’t look at the undo logs during start-up
Mode 6 – Doesn’t roll-forward from the redo logs (ib_logfiles) during start-up