Issue while opening SSRS Report with Oracle as Datasource in Report Manager

I deployed SSRS report in Report Manager but I am unable to generate that report. Am getting following error.

Is it problem with datasource in report manager? I am not able to change the Data source type to Oracle. It is showing Microsoft SQL Server. How can I change it, no other options are coming except Microsoft SQL Server. Please help.

• An
  error has occurred during report processing. (rsProcessingAborted)
  
  • Cannot
    create a connection to data source 'TEST_DS'. (rsErrorOpeningConnection)
    
    • For
      more information about this error navigate to the report server on the local
      server machine, or enable remote errors