VMS Help MACRO, VAX MACRO Assembler, Directives, .DEBUG  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Specifies that the symbols in the list are  made  known  to  the
    VAX Symbolic Debugger.

      .DEBUG symbol-list

    symbol-list

    A list of legal symbols separated by commas.

    During an interactive debugging session, you can use these symbols
    to refer  to  memory  locations or to examine the values assigned
    to the symbols.

    The assembler adds the symbols in the symbol list to the symbol
    table in  the  object  module.   You need not specify global
    symbols in the .DEBUG directive because global symbols are
    automatically put in  the object module's symbol table.