1.DBG> SHOW SOURCE
        no directory search list in effect
      DBG> SET SOURCE [PROJA],[PROJB],[PETER.PROJC]
      DBG> SHOW SOURCE
          source directory list for all modules,
          match the latest source file version:
              [PROJA]
              [PROJB]
              [PETER.PROJC]

      In this example, the SET SOURCE command specifies that the
      debugger should search directories [PROJA], [PROJB], and
      [PETER.PROJC], in that order, for the latest version of source
      files.

    2.DBG> SET SOURCE /EXACT
      DBG> SHOW SOURCE
          no directory search list in effect,
           match the exact source file
      DBG> SET SOURCE [JONES]
      DBG> SHOW SOURCE
          source directory list for all modules,
           match the exact source file version:
               [JONES]
      DBG> CANCEL SOURCE /EXACT
      DBG> SHOW SOURCE
           source directory list for all modules,
           match the latest source file version:
               [JONES]

      In this example, the SET SOURCE/EXACT command establishes a
      search method (exact version) that remains in effect for the
      SET SOURCE [JONES] command. The CANCEL SOURCE/EXACT command not
      only cancels SET SOURCE/EXACT command, but also affects the SET
      SOURCE [JONES] command.