Logical Unit of Work (LUW)

A Logical Unit of Work (LUW or database transaction) is an inseparable sequence of database operations which must be executed either in its entirety or not at all. For the database system, it thus constitutes a unit.

LUWs help to guarantee database integrity. When an LUW has been successfully concluded, the database is once again in a correct state. If, however, an error occurs within an LUW, all database changes made since the beginning of the LUW are canceled and the database is then in the same state as before the LUW started.

An LUW begins

• each time you start a transaction

• when the database changes of the previous LUW have been confirmed (database commit) or

• when the database changes of the previous LUW have been cancelled (database rollback)

An LUW ends

• when the database changes have been confirmed (database commit) or

• when the database changes have been canceled (database rollback)

Database commit and rollback

Within an LUW, database changes are not made until after a database commit. Prior to this, any database change can be canceled by a database rollback.

In the R/3 System, a database commit is triggered either automatically or by the ABAP/4 command COMMIT WORK or the appropriate Native SQL command for the database system.
Similarly, a database rollback is triggered either automatically or by the ABAP/4 command ROLLBACK WORK or the appropriate Native SQL command for the database system.

A database commit is triggered automatically by

• each screen change, and especially after the ABAP/4 commands CALL SCREEN, CALL DIALOG, CALL TRANSACTION, MESSAGE or

• a Remote Function Call

A database rollback is triggered automatically by

• errors which occur at runtime or

• the ABAP/4 command MESSAGE with the message type 'A'

After each database commit or rollback, the database locks set in the LUW are released (see Database Locking).