Details of OBSD partitioning program?

[Scott Ehrlich <scott@ehrlichtronics.com>]

I was recently introduced to
http://staff.washington.edu/jdlarios/autoclave/

but have yet to use it.  The description is simply that it wipes the
writable area of a hard drive to zeros.

What does OBSD's partitioning program do?   I've had troubles in the past
when a Linux primary partition has been removed but not the swap, and no
other partitioning tool other than OBSD's was able to handle and remove
that swap partition.

So, does OBSD's tool wipe out the drive, or simply mangle the partition
table enough to allow for proper repartitioning, keeping any existing data
in the writable area intact or at least untouched, even if "erased"?

Thanks.

Scott