The default initial heap is mapped at address
#x10000000
(0.25GB). LispWorks then tries to locate the location of dynamic libraries, and marks a region around these libraries that should not be used (by default 64MB from the bottom). In most cases this suffices to avoid clashes.
Problems can arise if the memory at
#x10000000
or above is already used by another part of the software. If that memory gets used before LispWorks is mapped, LispWorks must be relocated elsewhere, typically to a higher address.
If the memory above LispWorks gets used by other parts of the software after LispWorks was mapped, it may be possible to avoid the problem by reserving some memory above LispWorks by supplying ReserveSize .
LispWorks User Guide and Reference Manual - 21 Dec 2011