#include <db_cxx.h> int DbEnv::mutex_lock(db_mutex_t mutex);
        The DbEnv::mutex_lock() method locks the mutex allocated by 
        DbEnv::mutex_alloc().  The
         thread of control calling DbEnv::mutex_lock() will block until the
         lock is available.
    
         The DbEnv::mutex_lock() 
            
            
                method either returns a non-zero error value or throws an
                exception that encapsulates a non-zero error value on
                failure, and returns 0 on success.
            
        
    
The mutex parameter is a mutex previously allocated by DbEnv::mutex_alloc().
                         The DbEnv::mutex_lock() 
            
            
                method may fail and throw a DbException 
                exception, encapsulating one of the following non-zero errors, or return one
                of the following non-zero errors: