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 1   Overlays on a Network
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     .RTLink produces overlays containing compiled program code.  By default,
     all compiled Clipper code is placed in dynamic overlays.  Additionally,
     static overlaying may be requested for C or Assembler code.

     By default, overlays are appended to the end of the application's  .EXE
     file (the code may be written to a separate overlay file by using the
     INTO clause in the overlaying directive).  During execution, the runtime
     system opens the .EXE file and reads overlays as required.

     When the runtime system needs to read overlays, it opens the .EXE file
     for shared, read-only access.  On a network, this allows multiple
     processes to read the file at the same time.

     On some networks, however, a problem can arise if an attempt is made to
     run the .EXE when another process has opened it to read overlays.  The
     error occurs because the DOS EXEC function (used by COMMAND.COM to
     execute programs) opens .EXE files using a sharing mode called
     "compatibility mode."  On some networks, this causes a sharing violation
     if the file is already in use by another process, even if the other
     process has specified that it wishes to share the file.

     If this conflict occurs, it can usually be resolved by marking the
     affected file read-only on the disk.  A small utility program, RO.COM,
     is supplied for this purpose.  RO toggles the read-only status of a
     specified file.