Hi Rajani,
I think the configuration between your Portal (Java system) and BW backend system might be having some issues due to which you might be facing this issue.
I would recommend you to run the supportdesk tool following tne below SAP note which is for the configuration between Backend and Portal system.
If any configuration is incorrect it will report as RED entry and will propose a suggestion how to correct it.
SAP Note 937697 : Usage of SAP Netweaver BI Diagnostic & Supportdesk tool
Regards,
Amit