When :no-symbol-function-usage is true while delivering an image "foo" on x86 platforms, delivery writes a file named "foo.zaps" (the "zaps file") containing debug information about the symbols that were eliminated.
If an error occurs in the delivered image, the backtrace will contain a line of the form.
("SYMBOL-FUNCTION-VECTOR" nnn)
where nnn is an integer. The actual function name can be recovered from the zaps file by doing this in the LispWorks development image:
(require "delivery") (dv::recover-zapped-symbol-from-file "foo.zaps" nnn)
The numbers are unique to each image, so take care to use the zaps file that was produced at the same time as the delivered image.
Delivery User Guide - 01 Dec 2021 19:35:04