long running "alter table x drop unused columns checkpoint 10000;"

Hello,

I have a "alter table x drop unused columns checkpoint 10000;" running for the past 12 days. There is only one unused column in that table that is being dropped. The table has more than 14,725,000,000 records and according to dba_segments, is taking some 782 GB of storage (excluding indexes). Is there any way of knowing how far along the drop is or how many records are left to process?

Thank you,

Mark T.

P.S. Three days ago my desktop PC crashed and the drop column command got interrupted. So I resumed the operation with "alter table x drop columns continue;". I'm pretty sure that has no effect on the time it takes for the operation to complete (the documentation states "Specify