Slows up garbage collection during the execution of code that allocates a lot of space.
The forms for which you want the garbage collector to behave differently from normal.
The result of executing
is for use with code that allocates a lot of space but is not interactive. It ensures that garbage collection (GC) is carried out less frequently while these forms are being executed. However, each GC may take longer.
In LispWorks 5.0
is implemented only in 32-bit LispWorks. In version 5.1 and later it is implemented in 64-bit LispWorks as well.
LispWorks User Guide and Reference Manual - 21 Dec 2011