X157: Cannot obtain exclusive lock or drop lock in isolation level 5 or 6.

When working at isolation level 5 (dirty read) or level 6 (snapshot read), a transaction cannot acquire or drop exclusive locks on any database object. Levels 5 and 6 are intended for read only. You cannot insert, update, delete, or alter database objects at these levels. You can change the isolation level using the following command:

SET ISOLATION isolation-level