The Data Query is not available for use Once they are used for a particular graph Type in cacti?

Issue:
The Data Query  is not available for use Once they are used for a particular graph Type in cacti?

Resolution:
1. Delete the graph and when ask to delete the data sources. Please delete them.
2. If you have forgotten to do so Please go to "Data Sources" option under management.
3. Search the device there and delete the data sources related to that graph.