This section contains the following topics:

• Strongly typed compile time object:
  The binary description of the interfaces an R/3 component opens up is stored in a Type Library. The type library is part of the generated proxy objects, so that meta information from the R/3 system is available at design time as well as at runtime of the clients. This means that you can display the interface definition in the development environment. In addition, no round trips to the SAP system are necessary at runtime. This increases performance compared to those solutions that retrieve their meta data at runtime.
• ABAP data types are mapped automatically onto the corresponding OLE data types (and vice versa).
• Tables and structures from R/3 are represented by ADO Recordsets.
• COM versus RFC:
  Using DCOM between the client program and the MTS server allows you to distribute intranet applications without having to supply the SAP DLL and the appropriate OCX controls. In addition, there is no need for net-wide maintenance of services, samsg.ini and saprout.ini files.
• Dual interface:
  VB5 (and higher) or C++ can use it to access methods directy, that is by bypassing the Automation interface IDispatch.
  VB4 or the Scripting languages can access via IDispatch.
• Resource pooling allows an optimized administration of resources and a high performance of the R/3 accesses.
• There is no BOR runtime, since BAPIs are called directly via the call of the function modules that define them.
• DCOM Connector uses the security services of the MTS to guarantee access security.
• BOR names for methods, key fields, and parameters are transferred completely and case-sensitively.
• Generation of DCOM proxies and their installation in the MTS (as host for COM objects) is controlled via a user interface, the DCOM Object Builder. This allows you to minimize the effort required to generate DCOM proxies and to concentrate on programming the clients instead.
• The Object Builder supports also  the generation and installation of a session component.

Note

• Using the DCOM Connector Without MTS
  The new version of the DCOM Connector (as of Release 4.6A) allows you to use the generated business components without MTS as runtime environment as well. In this case, you need not install the MTS.
  However, keep in mind that you lose the advantages connected to the MTS such as resource pooling, security services, and so on.

The methods of business objects provided on the R/3 application server or the remote functions are available in the MTS via interfaces of the generated COM objects. The runtime environment of the DCOM Connector is responsible for generating and administering COM objects and thus allows you to call BAPIs or remote functions in the R/3 system. The DCOM Connector is based on the RFC protocoll and uses parts of the RFC API. In connection with the MTS, the DCOM Connector can use the mechanisms of resource pooling to efficiently administer RFC accesses. For this purpose, the DCOM Connector is installed in the form of components within a package in the MTS.
As the central tool for the interoperability between R/3 components (BAPIs and remote functions) and COM or HTML clients MTS provides functions for managing the R/3 access ("system location", "load balancing") as well as its own security concept ("MTS roles").
COM clients use the DCOM interface (1) to access MTS components. You can program them in VC++ or in VB (VBA) or in any other languages that support COM.
HTML clients (that is Web Browsers) establish the connection to the Internet Information Server (IIS) (2) via the HTTP protocoll. This connection goes with the call of an Active Server Page (ASP). ASP is installed in the Internet Information Server as Scripting machine. The Active Server Pages communicate with the MTS via DCOM to access its components. The scripts embedded in HTML, on the other side, are executed via ASP on the server side and returned to the Web Browser as HTML coding.
In addition, the Internet Explorer 4.0 can establish a direct connection to Remote Data Services (RDS) (3) via HTTP. RDS is a client-side technology that enables the client not only to display table data but also to change them directly.
RDS also uses DCOM to acces the components in the MTS. This connection is suited only for calling stateless objects.

Possible Scenarios for Using the DCOM Connector