Sams Teach Yourself SQL in 21 Days, Fourth Edition

A Frequent COMMIT Keeps the DBA Away

When performing batch transactions, you must know how often to perform a COMMIT statement. As you learned on Day 12, “Controlling Transactions,” a COMMIT statement finalizes a transaction. A COMMIT saves a transaction or writes any changes to the applicable table(s). Behind the scenes, however, much more is going on. Some areas in the database are reserved to store completed transactions before the changes are actually written to the target table. Oracle calls these areas rollback segments. When you issue a COMMIT statement, transactions associated with your SQL session in the rollback segment are updated in the target table. After the update takes place, the contents of the rollback segment are removed. A ...