>>>I tried tablerevert(.t.) but it does not work. I guess at the time of the error the current alias is "lost" and tablerevert() needs an alias to work with.
>>
>>Yes, switch to the right DS and try tablerevert and more importantly - rollback transaction.
>
>How do you switch to the right DS? Is there a comment that will show me list of DSs?

When you're in the command window, type set. You'll see all the datasessions which are currently opened.

You can also try

=asessions(laSessions)

for lnI = 1 to alen(laSessions)
   set datasession to (laSession[ln])
   && check if open transactions are there 
   if TXNLEVEL( ) > 0
      rollback transaction
  endif
next