A user issues the SET TRANSACTION...ISOLATION LEVEL EXCLUSIVE command while there are other concurrent user connections to the same database instance. In order to “lock” the database using the SET TRANSACTION...ISOLATION LEVEL EXCLUSIVE command, the user executing the command must have the only connection to the database.

Two or more users are connected to a database instance, and one of the users attempts to execute an ALTER TABLE...ADD CONSTRAINT command. For concurrency control reasons, you cannot add constraints to a table while other user sessions are active.

A Data Vault Loader operation is attempted on a database while one or more users are connected to the database instance. The Data Vault Loader requires exclusive access to the database in order to function.