#include <db.h> int DB_ENV->lock_id(DB_ENV *env, u_int32_t *idp);
         The DB_ENV->lock_id() method copies a
         locker ID, which is guaranteed to be unique in the environment's
         lock table, into the memory location to which 
         idp refers.
    
Note that lockers are not free-threaded; lockers can not be used by more than one thread at the same time.
The DB_ENV->lock_id_free() method should be called to return the locker ID to the Berkeley DB library when it is no longer needed.
         The DB_ENV->lock_id() 
            
                  method returns a non-zero error value on failure and 0 on success.