XFD files contain the data dictionary used to map the SQL from your Windows application to the appropriate I/O requests.
The following sections describe the rules followed by AcuODBC to locate the data dictionary files. There are some general rules and the some rules specific to remote file access.
General Rules
Data dictionary files must be located in the directory specified in the XFD Directory field on the General tab of the AcuODBC Configuration property sheet. The AcuODBC driver looks for an XFD file with the same base name as the table. In this instance, the driver does not differentiate between uppercase and lowercase letters nor between hyphens and underscores.
The name of each file corresponds to the name used in the SELECT clause of the COBOL program, followed by the "XFD" extension. See section 6.2.5, "Naming the XFD File" for more information.
To locate an XFD file, AcuODBC needs the DSN and table names. If the data source is part of a master DSN, AcuODBC uses the XFD directory specified for the master DSN. If you have defined an alias on the File Alias tab of the AcuODBC Configuration property sheet, the XFD file is accessed through the name of the alias, not the original name of the file. See section 3.8, "Multicompany Support" and section 3.7, "File Aliases" for more information.
If the AcuODBC driver cannot find the XFD file in any of these places, it looks for WHEN condition tables.
Finally, if the driver does not find the XFD files in any of these places, you receive an error message indicating that the table was not found. In addition, should you have duplicate table names, the driver finds the XFD file, but the table it refers to is undefined; that is, you cannot know which of the duplicate tables it defines.
Remote File Access
Using a remote file server, you can locate data dictionary files on the remote server, but this is not necessary. This is a feature you can use at your convenience.
A sequential ASCII file called "xfdrmt.dir" (lowercase) must be stored in the remote directory. This file must contain as many lines as the number of XFD files in that directory. Each line must be filled with the name of each data dictionary file. For an example of the "xfdrmt.dir" file, please refer to section 3.2, "Defining the Data Source".