A data processing apparatus is provided that includes monitor circuitry to produce local trace data indicating behaviour of the data processing apparatus. Interface circuitry communicates with a second data processing apparatus and encoding circuitry produces an encoded instruction to cause the local trace data to be stored in storage circuitry of the second data processing apparatus or to be output at output circuitry of the second data processing apparatus. The interface circuitry transmits the encoded instruction to the second data processing apparatus.