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.
LispWorks Delivery User Guide - 10 Aug 2017