Messages with severity level 13 indicate that something is wrong with the current user-defined transaction.
For example, the user may have issued a commit transaction command without having issued a begin transaction, or they may have tried to roll back a transaction to a savepoint that has not been defined (sometimes there may be a typing or spelling mistake in the name of the savepoint).
Severity level 13 can also indicate a deadlock, in which case the deadlock victim’s process is rolled back. The user must restart his or her command.