VMS Help DEBUG, Qualifiers, /KEEP  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Invokes the kept debugger. The kept debugger includes a Run/Rerun
    capability that allows you to debug an image multiple times or
    debug a series of distinct images without exiting the debugger.

    Issuing the DEBUG/KEEP command is the only way to invoke the kept
    debugger.