Internal symbols in packages you have kept may still be shaken out. If any such symbol must be kept in the application, retain it force in one of the following four ways:
This is the recommended solution. See :keep-symbols.
This solution is suitable when all the symbols to keep are in one package,
. See :never-shake-packages.
External symbols are always shaken during delivery.
You can override this behavior by passing
. See :shake-externals.
You can also specify :packages-to-shake-externals and :packages-to-keep-externals.
A reference from the object to the symbol ensures that the garbage collector passes over it during delivery.
See also Coping with intern and find-symbol at runtime.
LispWorks Delivery User Guide - 13 Dec 2011