User`s guide

Remarks
Lock requests can be nested and each request will increase the lock count
by 1. For every request, you will need a release from the same I/O
interface (see SYSTem:LOCK:RELease command).
Instrument locks are handled at the I/O interface level (GPIB, USB, LAN,
etc.) and you are responsible for all coordination between threads and/or
programs on that interface.
When a request is granted, only I/O sessions from the present interface
will be allowed to change the state of the instrument. From the other I/O
interfaces, you can query the state of the instrument but no measurement
configuration changes or measurements are allowed.
Locks from LAN sessions will be automatically released when a LAN
disconnect is detected.
When a lock is granted, Bit 10 in the Standard Operation Register will be
set (see STATus:OPERation:CONDition? command). In addition, the entire
instrument front panel, including the Local key, will be locked out while a
lock is in place ("KEYBOARD LOCKED" is displayed).