If you get an error message like “Unknown Period Type (M) , (D) or (Y)” then you should first check the related SAP standart background jobs like mentioned below…

There is an example error message getting “Unknown Period Type (M)” during ST03 operation ;

Double click the message and get the detail info

Now first of all we should check the background job “SAP_COLLECTOR_FOR_PERFMONITOR” status

If “CANCELED” then we can try to execute “RSCOLL00″  program manually

After this please try ST03 tcode again and now ST03 probably work without any problem like below