MULTILEVEL TRANSACTION RECOVERY IN A DATABASE SYSTEM WHICH LOSS PARENT TRANSACTION UNDO OPERATION UPON COMMIT OF CHILD TRANSACTION

When a subtransaction (46) of a higher-level transaction (50) commits during the operation of a database (10), the database enters into its operation log a record (FIG. 6 ) that acts both as a commit record for the subtransaction (46) and as an update record for the higher-level transaction and includes a field (74) that identifies a higher-level "undo" transaction whereby the subtransaction can be undone without individually undoing its constituent operations. By logging operations in this manner, the database can handle multi-level recovery with very few restrictions on the timing of its updates and log entries.