The XPART command processes an XGP file to determine which characters it uses
in each font, and  sets up partial-font-loading switches  in the file.   This
lets the spooler make better  use of the limited  core available to the  font
compiler, such that documents using  several large fonts may be  successfully
spooled.

You can  also give  a list  of  pages, in  which case  only those  pages  are
retained.  Partial font-loading is based on the characters used in the  pages
selected.  Note that, if only a few pages are to be spooled from a large  XGP
file, processing the file with XPART to get the selected pages will result in
a more accurate (higher) priority in the spooler's queue.

Command format  is XPART  OUTPUT←INPUT(pages).   Default extension  is  .XGP,
default output is the same as the input name but on the current (alias)  ppn.
For more details READ XPART.