This variable sets the file format on a file-by-file basis. Replace filename with the base name of the file (the filename minus directory and extension). The meaning of the variable is the same as for V_VERSION. This variable is useful if you want to have all your files in one format, with a few exceptions. For example, you might want to maintain most of your files in Version 6 format, but have a few files in an earlier version to conserve file handles. Note that this variable affects the file format only when it is created. You can always rebuild the file in another format later.
This variable (and the V_VERSION variable) is most helpful when you are using transaction management. The transaction system does not record the format of the created file if an OPEN OUTPUT is done during a transaction, because the transaction system is not tied to any particular file system. If you need to recover a transaction, the system will recreate the OPEN OUTPUT files using the settings of the VERSION variables.