When a Format 5 DISPLAY statement is specified, the value stored in
  envlog-name is moved to environment-name. See ENVIRONMENT-NAME in
  the SPECIAL-NAMES paragraph. The updated value of environment-name
  becomes the environment variable or logical to be accessed by
  subsequent Format 6 DISPLAY and Format 8 ACCEPT statements.

  Format 5 -

   DISPLAY envlog-name UPON environment-name
      [ END-DISPLAY ]