DECset commands pertain to the use of the DECset Environment Manager
  in a character-cell terminal environment or in batch mode.

1  –  SET

  The SET command allows you to set the current `context' or the
  current context database for your process.

  A `context' is a named set of values that tailors the DECset tools
  to a specific software development activity (for example, fixing
  bugs or implementing enhancements).

  The SET command line has one of the following forms, depending upon
  whether a context or a context database is being set:

       DECSET SET CONTEXT context-name [/DATABASE=database-file]

       DECSET SET DATABASE database-file

  DCL wild cards may not be used in either the context-name or
  database-file argument.

  The /DATABASE qualifier allows you to set a context that is defined
  in the specified database.  If the /DATABASE qualifier is missing,
  the value of the DECSET$CONTEXT_DB logical name is used; if this
  logical name is undefined, your SYS$LOGIN directory is searched for
  a file named DECSET$KNOWN_CONTEXTS.DECSET_CONTEXT_DB.  If a database
  cannot be located, an error message is displayed.

  The DECSET SET CONTEXT command automatically defines the logical names
  DECSET$CONTEXT and DECSET$CONTEXT_DB.  The DECSET SET DATABASE command
  automatically defines the logical name DECSET$CONTEXT_DB.

2  –  SHOW

  The SHOW command is used to display either the description of a
  single `context' or the file specification of the current context
  database.

  A `context' is a named set of values that tailors the DECset tools
  to a specific software development activity (for example, fixing
  bugs or implementing enhancements).

  The SHOW command line has one of the following forms, depending upon
  whether information about a context or a context database is being
  shown:

       DECSET SHOW CONTEXT [context-name] [/DATABASE=database-file]

       DECSET SHOW DATABASE

  DCL wild cards may not be used in either the context-name or
  database-file argument.

  If context-name is not specified in the DECSET SHOW CONTEXT command,
  the value of the DECSET$CONTEXT logical name is used (if that logical
  name is defined).  If the context name cannot be determined, an error
  message is displayed.

  The /DATABASE qualifier allows you to show information about a
  context that is defined in the specified database.  If the /DATABASE
  qualifier is missing, the value of the DECSET$CONTEXT_DB logical name
  is used; if this logical name is undefined, your SYS$LOGIN directory
  is searched for a file named DECSET$KNOWN_CONTEXTS.DECSET_CONTEXT_DB.
  If a database cannot be located, an error message is displayed.