luw

[Former Member]

what is luw. Plz explain a bit. and where do we use it

[Former Member]

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. If an SAP LUW contains database changes, you should either write all of them or none at all to the database. To ensure that this happens, you must include a database commit when your transaction has ended successfully, and a database rollback in case the program detects an error. However, since database changes from a database LUW cannot be reversed in a subsequent database LUW, you must make all of the database changes for the SAP LUW in a single database LUW. To maintain data integrity, you must bundle all of you database changes in the final database LUW of the SAP LUW.

<b>Database LUW vs. SAP LUW</b>

In the case of the database, an LUW is a sequence of data operations that cannot be divided up. The operations are either carried out in full or not at all. Database LUWs are modules that make up the database procedures for consistent data processing.

By way of contrast, an LUW for the SAP System is a business process, which cannot be divided up. The process is either executed in full or not at all. An SAP LUW usually must include several database LUWs (see graphic above), each of which can be terminated with a database COMMIT, which is generated automatically. Under normal circumstances, the SAP LUW contains a dialog part (which maps a business process), and the command for writing the data to the database (update part).

In each database LUW, data is written to the database to special update tables (and not to the application tables). Once the dialog part has been completed, all of the data in a database LUW is transferred into the application tables: the update request is then performed.

Have a look at below link.

http://help.sap.com/saphelp_nw04/helpdata/en/41/7af4bfa79e11d1950f0000e82de14a/content.htm

Best Regards,

Vibha

*Please mark all the helpful answers

[Former Member]

Hi Abhay,

Find some more details about SAPLUW and DBLUW.

<b>What is LUW or Database LUW or Database Transaction ?-</b> A “LUW” ( logical unit of work ) is the span of time during which any database updates must be performed . Either they are all performed ( committed ) , or they are all thrown away ( rolled back ).

<b>LUW ( or “database LUW” or “database transaction” )</b>

This is the set of updates terminated by a database commit. A LUW lasts, at most, from one screen change to the next ( because the SAP system triggers database commits automatically at every screen change ).

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.

<b>An LUW begins</b>

- 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)

<b>An LUW ends</b>

- When the database changes have been confirmed (database commit) or

- When the database changes have been canceled (database rollback)

<b>What is SAP LUW or Update Transaction ?-</b> Update transaction ( or “SAP LUW”)

This is a set of updates terminated by an ABAP/4 commit. A SAP LUW may last much longer than a database LUW, since most update processing extends over multiple transaction screens.The programmer terminates an update transaction by issuing a COMMIT WORK statement.

<b>Does the external program run in the same SAP LUW as the caller, or in a separate one?</b>

- Transactions run with a separate SAP LUW

- Reports run with a separate SAP LUW

- Dialog modules run in the same SAP LUW as the caller

- Function modules run in the same SAP LUW as the caller

The only exceptions to the above rules are function modules called with IN UPDATE TASK (V2 function only) or IN BACKGROUND TASK (ALE applications). These always run in their own (separate) update transactions.

Reward Points if this Helps.

Manish

[Former Member]

hi,

Check this threads

LUW

Let one user is modifying a record and the second user is trying to delete the same record at the same time.

If the second user is successful in deleting the record, then the first user will face problem in modifying the record.

To avoid such problems, SAP has introduced LUW (Logical unit of Work)

LUW is defined as Locking Mechanism to protect transaction integrity.

Types of LUWs:

Database transaction or LUW.

Update transaction or SAPLUW.

ABAP/4 Transaction.

database transaction

Database transaction or LUW is defined as a period in which operation requested must be performed as one unit.

At the end of LUW, either the database changes are committed or rolled back.

SAP LUW

One SAP LUW can have several databases LUW. So a set of database transactions either committed or rolled back.

The special ABAP/4 command ‘Commit work’ marks the end of SAP LUW.

ABAP/4 Transaction

It is made up of a set of related task combined under one transaction code.

ABAP/4 transaction functions like one complete object containing screens, menus and transaction code.

Regarsd,

Sailaja.

[Former Member]

Hi,

Please follow the links,

http://help.sap.com/saphelp_nw04/helpdata/en/41/7af4bfa79e11d1950f0000e82de14a/content.htm

http://help.sap.com/saphelp_nw04s/helpdata/en/e5/de86d835cd11d3acb00000e83539c3/content.htm

good pdf

http://www.sappressbooks.com/downloads/h958_preview.pdf

weblog

/people/jens.seifert/blog/2006/09/29/new-features-in-db2-9-for-luw--auto-reorg

http://www.dbis.ethz.ch/research/publications/19.pdf

Please reward for the same