Microsoft Office Tutorials and References
In Depth Information
Let’s see at a high level how all these components are connected. As you can see in Figure 4-7 , there are three
major participants—Business Connectivity Services, External Systems, and Rich Client Office applications.
Note, however, that BCS is the connector for the other two layers.
Figure 4-7. BCS high-level overview
Business Connectivity Services Layer
The BCS layer consists of two major blocks, the BDC Metadata Store and the BCS Client Cache. To understand what
the BDC Metadata Store is, you need some background information. The BDC model contains metadata related to
external content types, database connections, and so on. It actually enables the API of an external system described
in the metadata model with a much simplified BDC object model. A metadata model contains real information about
methods, entities, and so forth, such as employee data, customer information, and sales orders.
BDC models are stored in SQL Server database tables and are loaded into memory before the BDC runtime 5 can
use them. To perform operations such as load, modify, and so on, you make use of stored procedures. All these pieces
form the BDC Metadata Store.
The BCS Client Cache essentially copies the external system data from the server and caches it for Office client
solutions in the SQL Server Compact Edition database on the basis of per-user instances on the client computer.
This facilitates the automatic copying and linking of client data with external systems either manually or by automatic
synchronization, thus avoiding heavy transactions between the client and server data and improving the throughput
of the application. This caching mechanism also enables offline disconnected mode.
5 You will learn more about the BDC runtime later in this chapter.
 
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