Siemens SINUMERIK Commissioning Manual page 77

If an operation (copy, delete, edit) is active on the drive at the time of the TCU switchover,
the display is retained until the action is finished. The display is not updated until the
operation is finished.
Note
Because the TCU is connected to the PCU via a network connection, the response times
depend on the particular network. Executing a part program (EXTCALL) from USB memory
is not recommended.
If a USB drive is disconnected while data are being written to or read from this drive, data
loss can result.
HMI Advanced (IM4)
Commissioning Manual, 03/2009, 6FC5397-0DP10-3BA0
Configuring the HMI system
2.3 Connecting network drives
71