This variable defines a series of directories to search for XFD files, rather than indicating only one (as in XFD_DIRECTORY). Each directory is searched in order until an XFD matching the name of the file is found. Once a file with the same name is found, the runtime stops searching, even if other files of the same name are located in a subsequent directory in the search parameter. Only named directories are searched, not subdirectories.
The default for XFD_PREFIX is empty. If this variable is set to any other value, the configuration variable XFD_DIRECTORY (in which you specify only one directory) is ignored. You can specify a directory path that contains embedded spaces if you surround the path with quotation marks. Separate entries using a semi-colon (;). For example:
XFD_PREFIX C:\ "Sales Data";C:\Customers
You may specify up to 4096 characters for this variable.