The provider's function accepts as input the metricid, userword, calltype and datasize it passed at registration time, as well as the return buffer obtained for its use by Performance Services. The DCI_SPI_RPC method is the only method supported by the dciEZRegister API. The DCI_SPI_RPC method only supports the calltype of DCI_GETDATA. Performance Services keeps a table with the metricid, metricidstr, function address, userword, calltype, and datasize passed at registeration time which is checked by Performance Services during a data request.