Sony MSW-900 Supplemental Operation Manual page 135

Message related to mis-operation
"INVALID OPERATION"
The message appears when you push the ASSIGN 1 switch before you
start recording. The operation is invalid.
Confirming the remaining capacity on the memory
3
label and clearing recorded data
For detailed information, refer to "To confirm the remaining capacity on
the memory label" and "To clear recorded data" in "Recording the
Recording Start Time Code onto the Memory Label - Tele-File"
described in the Operation Manual supplied with a camcorder.
3-5
Chapter 3 Recording a Tele-File Mark