#include <db.h> u_int32_t DB_TXN->id(DB_TXN *tid);
         The DB_TXN->id() method returns the unique transaction id associated
         with the specified transaction.  Locking calls made on behalf of this
         transaction should use the value returned from DB_TXN->id() as the
         locker parameter to the DB_ENV->lock_get()  
         or DB_ENV->lock_vec()  calls.