DECC$FILE_PERMISSION_UNIX

   With DECC$FILE_PERMISSION_UNIX enabled, the file permissions
   for new files and directories are set according to the file
   creation mode and umask. This includes mode 0777. When an earlier
   version of the file exists, the file permissions for the new file
   are inherited from the earlier version. This mode sets DELETE
   permission for a new directory when WRITE permission is enabled.

   With DECC$FILE_PERMISSION_UNIX disabled, modes 0 and 0777
   indicate using RMS default protection or protection from the
   previous version of the file. Permissions for new directories
   also follow OpenVMS rules, including disabling DELETE
   permissions.