The flow chart in the following figure illustrates the DataServer's internal logic.
Figure 2. DataServer logic
As shown in the figure above, when you execute an application that accesses a MS SQL Server database, the compiler translates ABL or SpeedScript statements into their SQL equivalents. The DataServer then issues the SQL statements to the ODBC driver through the ODBC API. The driver, which provides the software mechanisms for accessing and controlling the data source, processes the SQL statements, transfers them to the data source manager, and returns the results to OpenEdge through the ODBC API.
Note: The SQL presented in the figure has been simplified for the purpose of focusing on the data flow.
To facilitate the flow of statements between client and server, the DataServer places OpenEdge equivalents for data definitions from a supported data source into a schema holder (a repository for data definitions for one or more MS SQL Server data sources). When the OpenEdge client or WebSpeed Agent executes statements and retrieves information from the data source, it relies on data definitions in the schema holder.
