Transaction 

A transaction is a series of database operations that form a unit with regard to data backup and synchronization.

Transactions close with COMMIT or ROLLBACK:

Changes closed with a COMMIT can no longer be reversed with a ROLLBACK.

A new transaction is implicitly opened as a result of both a COMMIT and a ROLLBACK.

See also:

Reference Manual: SAP DB 7.2 and 7.3 ® Transactions.