HI,
  I created DCI "Net.Interface.BytesIn(*)",* is the index of interface,and selected "Delta value(average per second)".I use the method "Session.queryParameter()" (Java API version 1.1.6),the result returned is the total number of bytes-in ,not delta value average per second ,I've also viewed the origin data in database and it is exactly delta value per second,why??

Hi!

Because delta calculation is done by server after data obtained from node as part of DCI processing. When you do queryParameter call, it just reads raw value from end node - it is not related to any DCI. You either have to do delta calculation by yourself or use another API call to get last values of particular DCI.

Best regards,
Victor

thank you,I've tried fetching the last value in database using getDciDataRow,and it worked fine