As noted in the previous section, a schema holder contains information about one or more supported ODBC data sources. This information, called the schema of the data source, is a description of its structure, its tables, the fields within its tables, and its indexes.
An application accesses the schema holder only when it compiles procedures and at the beginning of a run-time session for schema caching (the loading of data definitions into memory). Typically, the schema holder is not accessed during a run-time session after the initial schema caching.
Before an OpenEdge client can access data in the relevant ODBC data source, you must create a schema holder and load the required data source definitions into the schema holder. You can then use the Data Dictionary to add OpenEdge database features such as validation expressions and messages.
The following figure illustrates the schema-loading process.
Figure 3. The schema-loading process
If you plan to use the DataServer to send SQL statements directly to the data source using only the RUN STORED–PROCEDURE syntax and you do not expect returned data, you need not load data definitions into the schema holder; however, you must do the following:
Load the stored procedure into the schema holder
Connect to a data source
For information on using RUN STORED–PROCEDURE, see Stored procedures.
Load the stored procedure into the schema holder