1. Within a transaction, subtransactions can be defined which let a series of database operations within a transaction appear as a unit with regard to modifications to the database.
2. SAVEPOINT defines a position, i.e., the starting point for a subtransaction within a transaction, and assigns a name to this position. Any modifications made in the meantime can be rolled back by using ROLLBACK TO SAVEPOINT with a specification of the name, without influencing database operations that were performed within the transaction before this subtransaction.
3. Subtransactions have no influence on locks. These are only released by COMMIT or ROLLBACK. COMMIT or ROLLBACK implicitly close all subtransactions.