ABAP Keyword Documentation → ABAP Programming Guidelines → Architecture → Data Storage

Client Handling

Other versions: 7.31 | 7.40 | 7.54

Background

A client indicates a data area in an AS ABAP database that contains independent application data. The application data of different clients use the same database tables, but are flagged with a three-figure client ID within these tables.

When logging on to AS ABAP, this client ID must be entered. This selects the client whose data is processed by the user session. The current client is entered in the system field sy-mandt.

Open SQL statements support automatic client handling by default, where the data of the current client is accessed by default. This is specified by passing an implicit condition for the current client to WHERE conditions, and ignoring clients specified in modifying statements in work areas. Automatic client handling in Open SQL can be switched to a different client using the addition USING CLIENT or switched off using the addition CLIENT SPECIFIED.

Native SQL does not implement automatic client handling. The client in question does not need to be selected explicitly when Native SQL is used to access client-specific database tables or views.

Rule

Do not access the data of other clients

In the persistency services of business applications, access the data of the current client only.

Details

Each client within the application server is to be viewed as a self-contained unit. The additions USING CLIENT and CLIENT SPECIFIED should not be used in Open SQL statements of business applications. When Native SQL is used, only the current client should be selected.

The system field sy-mandt does not generally need to be evaluated, unless Native SQL is used to access client-specific database tables or views. The client ID is then needed to select the data of the current client explicitly.

Notes

Cross-client database tables (tables without client ID) are usually system tables. This means that cross-client access to these tables is also reserved for system programs.

If Open SQL has to be used to access data in a different client, USING CLIENT should be used instead of the addition CLIENT SPECIFIED, since all necessary conditions are set implicitly and accessing client-specific CDS views is more simple.

Bad example

The following source code shows an Open SQL access to a database table where the current client is specified explicitly. This makes a further explicit WHERE condition necessary. The system field sy-mandt cannot be specified directly when using the addition USING CLIENT.

SELECT SINGLE ...
       FROM dbtab CLIENT SPECIFIED
       WHERE mandt = @sy-mandt AND
             ...
       INTO ...

Good example

The following source code shows how Open SQL is generally used for implicit automatic client handling.

SELECT SINGLE ... 
       FROM dbtab 
       WHERE ... 
       INTO ...