I found a great Reference in DBA to DBA, which outlines how to view the status of the reorg.
Killing a reorg is a fairly simple matter, on the face of it, inasmuch as that you can just kill the reorg process and you're "done".
The problem is that you may have to rebuild indexes after this, for reasons that should be obvious.
Per Alexander Ashkenazi, If you cancel it during SORT or BUILD phase, your REORG will roll back. It shouldn't take long, because nothing has changed in your table at this point.
If your REORG fails for whatever reason during "RECREATE ALL INDEXES" phase, all or some of your indexes will be gone, but DB2 will start automatically rebuilding them on the first usage of the table.