Different types of LUWs. What r they?
Two types of LUW are:
DB LUW
A database LUW is the mechanism used by the database to ensure that its data is always
A database LUW is the mechanism used by the database to ensure that its data is always
consistent. A database LUW is an inseparable sequence of database operations that ends with a database
commit. The database LUW is either fully executed by the database system or not at all. Once a database
LUW has been successfully executed, the database will be in a consistent state. If an error occurs within a
database LUW, all of the database changes since the beginning of the database LUW are reversed. This
leaves the database in the state it had before the transaction started.
SAP LUW
A logical unit consisting of dialog steps, whose changes are written to the database in a single
A logical unit consisting of dialog steps, whose changes are written to the database in a single
database LUW is called an SAP LUW. Unlike a database LUW, an SAP LUW can span several dialog steps, and
be executed using a series of different work processes.
Database Logical Unit of Work (LUW)
From the point of view of database programming, a database LUW is an inseparable sequence of database operations that ends with a database commit. The database LUW is either fully executed by the database system or not at all. Once a database LUW has been successfully executed, the database will be in a consistent state. If an error occurs within a database LUW, all of the database changes since the beginning of the database LUW are reversed. This leaves the database in the state it was in before the transaction started.
The database changes that occur within a database LUW are not actually written to the database until after the database commit. Until this happens, you can use a database rollback to reverse the changes. In the R/3 System, database commits and rollbacks can be triggered either implicitly or using explicit commands.
Implicit Database Commits in the R/3 System
A work process can only execute a single database LUW. The consequence of this is that a work process must always end a database LUW when it finishes its work for a user or an external call. Work processes trigger an implicit database commit in the following situations:
· When a dialog step is completed Control changes from the work process back to the SAP GUI.
· When a function module is called in another work process (RFC). Control passes to the other work process.
· When the called function module (RFC) in the other work process ends. Control returns to the calling work process.
· When a WAIT statement interrupts the work process.
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