SAP's Open SQL

ABAP/4 code is portable between databases. To access the database in an ABAP/4 program you will code SAP's Open SQL. Open SQL is a subset and variation of ANSI SQL. The ABAP/4 interpreter passes all Open SQL statements to the database interface part of the work process (see Figure 1.27). There, they are converted to SQL that is native to the installed RDMS. For example, if you were running an Oracle database, your ABAP/4 Open SQL would be converted by the database interface to Oracle SQL statements.

If you use Open SQL, your SQL statements will be passed to the database interface. Using Open SQL has three main advantages. All of these advantages are implemented via the database interface.

PortabilityThe first advantage is the fact that your SQL statements will be portable between databases. For example, if for some reason your company wanted to switch from an Oracle to an Informix database, it could change the database, and your ABAP/4 code would continue to run without modification.

Buffering Data on the Application Server
Secondly, the database interface buffers information from the database on the application server. When data is read from the database, it can be stored in buffers on the application server. If a request is then made to access the same records, they would already be on the application server, and the request is satisfied from the buffer without having to go to the database. This buffering technique reduces the load on the database server and on the network link between the database and application servers, and can speed up database access times by a factor of 10 to 100 times.

Automatic Client Handling
The third advantage of using Open SQL is automatic client handling. With Open SQL, the client field is automatically populated by the database interface. This gives your development and testing teams many advantages, such as the ability to perform multiple simultaneous testing and training on a single database without interference from each other.