Hi Simon,
Mark is correct it is not support to do direct update to system table.
Some more information is that load optdiag from different version and different platform
only have limited support.
Changing statistics with optdiag
Some curiosa optdiag use bulk insert to insert the values in to the system tables this mean you need to handle the structure of the table at the client so we would not recommend to do this with normal BCP then the extra complexity is that system table change between version so great care have to be taken if this load is between different versions.
Niclas