Hi Priya
This can happen if there is a blocked query on database level. Before doing the upgrade, please ensure all jobs are paused, all services are stopped and anything else that could be accessing the database (such as BO reporting - customizations, any integrations with third party tools), are stopped as well. Confirm with your DBA nothing is running and then try the upgrade again.
If you are still getting an issue, please raise a Support case for us to take a look.
Kind Regards -Nika