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By running the below query we can find that which query is causing to the locking. SELECT lok.resource_type ,lok.resource_subtype ,DB_NAME(lok.resource_database_id) ,lok.resource_description ,lok.resource_associated_entity_id ,lok.resource_lock_partition ,lok.request_mode ,lok.request_type ,lok.request_status ,lok.request_owner_type ,lok.request_owner_id ,lok.lock_owner_address ,wat.waiting_task_address ,wat.session_id ,wat.exec_context_id ,wat.wait_duration_ms ,wat.wait_type ,wat.resource_address ,wat.blocking_task_address ,wat.blocking_session_id ,wat.blocking_exec_context_id ,wat.resource_description FROM sys.dm_tran_locks lok JOIN sys.dm_os_waiting_tasks wat ON lok.lock_owner_address = wat.resource_address    

If you are trying to change the name of the server in a production environment you need to look at the below steps. Please check whether Replication, Log shipping, Mirroring is installed. If that is the case, you should be cautious before you are running this script. You need to disable all these before you are going to run the below command. And also ensure that you have a backup of all the databases available. And follow the below steps. If you are trying to change the "Default Instance" you can run the below command.  

READ UNCOMMITTED is the least restrictive isolation level because it ignores locks placed by other transactions. Transactions executing under READ UNCOMMITTED can read modified data values that have not yet been committed by other transactions; these are called "dirty" reads. READ COMMITTED is the default isolation level for SQL Server . It prevents dirty reads by specifying that statements cannot read data values that have been modified but not yet committed by other transactions. Other transactions can still modify, insert, or delete data between executions of individual statements within the current transaction, resulting in non-repeatable reads, or "phantom" data. REPEATABLE READ is a more restrictive isolation leve l than READ COMMITTED. It encompasses READ COMMITTED and additionally specifies that no other transactions can modify or delete data that has been read by the current transaction until the current transaction commits. Concurrency is lowe...