Use the COMPRESS command to reorganize the contents of  a  dictionary
  file.   The new dictionary file will probably be smaller than the old
  file, since only the directories and data definitions are copied, not
  the   unused   free  space.   Only  valid  dictionary  files  may  be
  compressed.  You must  use  the  FIX  command  to  repair  a  corrupt
  dictionary file before you can compress it.

  To compress the main dictionary file, you  need  VMS  SYSPRV  or  VMS
  BYPASS privilege.  To compress a subdictionary file, you need only be
  the owner of the file.

  Command Syntax:

  COMPRESS input-file-specification output-file-specification

1  –  parameters

  input-file-specification

  Names the dictionary file you want to copy.  It  is  a  standard  VMS
  file  specification.   Wildcards are not permitted.  The default file
  extension is .DIC.

  output-file-specification

  Names  the  new  dictionary  file.   It  is  a  standard   VMS   file
  specification.   Wildcards  are  not  permitted.   The  default  file
  extension is .DIC.  You can use the same name for the output file and
  the  input  file.   If  you  do,  CDDV  creates an output file with a
  version number one higher than that of the input file.