Depending on how an SAP transaction is programmed, it can carry out database changes directly without using the SAP update system. The database changes are made at the end of a database LUW.

The transaction can, however, also use the SAP update system and bundle the updates of several database LUWs.

Bundling is the ABAP programming practice of collecting database changes and executing them all together at the end of a transaction. For more information, see Update Techniques.

Bundling updates involves combining important changes made by an SAP transaction in a database LUW. Only changes that are performed in a single database LUW can be reversed. If it is important to be able to reverse all of the changes made with an SAP transaction for the sake of maintaining data consistency, all of the changes must be bundled in one database LUW.

Bundling is implemented by postponing the processing of the special ABAP forms and function modules that make database updates. Processing of the bundled update forms and function modules is triggered only when the ABAP COMMIT WORK command is issued.

The SAP System also features its own locking mechanism for restricting data access. This mechanism is used partly to hold SAP locks within an SAP transaction beyond the boundaries of database LUWs. (At the start of a new database LUW, the database locks held by the previous LUW are released. The SAP locks, however, remain active).

Update bundling and the SAP lock system maintain data integrity in processes that cover several database LUWs, and fulfill the requirements regarding rollback. This means, all changes to data can be rolled back in the event of a runtime error during updating.