Why is DB_LOCK commented out in dbopen.3?

I see it is used in the libc/db code.

I am curious about it.

I am trying to track down why repeatedly opening my hash database with a 
parent and child processes with O_EXLOCK doesn't block when one of the 
processes has it open. (I posted about that to netbsd-help.)

I was wondering if DB_LOCK could help, but I see it looks to be for recno 
and btree only.

  Jeremy C. Reed