A recoverable schedule is one where, for each pair of transactions Ti and Tj such that Tj reads data items PREVIOUSLY written by Ti, the COMMIT operation of Ti appears before the commit operation of Tj. Recoverable schedules are desirable because failure of a transaction might otherwise BRING the system into an irreversibly INCONSISTENT state. Nonrecoverable schedules may sometimes be needed when updates must be made visible early due to time constraints, even if they have not yet been COMMITTED, which may be required for very long duration transactions.

A recoverable schedule is one where, for each pair of transactions Ti and Tj such that Tj reads data items previously written by Ti, the commit operation of Ti appears before the commit operation of Tj. Recoverable schedules are desirable because failure of a transaction might otherwise bring the system into an irreversibly inconsistent state. Nonrecoverable schedules may sometimes be needed when updates must be made visible early due to time constraints, even if they have not yet been committed, which may be required for very long duration transactions.