Hi Atul,
The user sessions are not killed in BI is one of the known issues in Business Objects. Please refer following documents to kill the sessions manually or automate the kill session process.
https://websmp130.sap-ag.de/sap(bD1lbiZjPTAwMQ==)/bc/bsp/sno/ui_entry/entry.htm?param=69765F6D6F64653D3030312669765F7361…https://websmp130.sap-ag.de/sap(bD1lbiZjPTAwMQ==)/bc/bsp/sno/ui_entry/entry.htm?param=69765F6D6F64653D3030312669765F7361706E6F7465735F6E756D6265723D3230313834383926
How to Delete Stale BI4 User Sessions with biUserSessionKillScript
Regards,
Hrishikesh