# MX\_QLOCK, MX\_QUNLOK > [HTML Version](mx_q_lock_unlok.htm) **xcall MIAMEX, MX\_QLOCK** **xcall MIAMEX, MX\_QUNLOK** MX\_QLOCK (MIAMEX 67) locks the qflock.sys file. It should be called before trying to read the qflock.sys file, and should then be followed by MX\_QUNLOK. MX\_QUNLOK (MIAMEX 68) removes the lock on the qflock.sys file which was placed by a prior call to MX\_QLOCK.