Seaquel
SQL Server error code

SQL Server error 1991

SQL Server raises error 1991 at severity 16, which marks a problem with the query or data that you can correct.

Cannot disable clustered index '%.*ls' on table '%.*ls'. Permission denied to disable foreign key '%.*ls' on table '%.*ls' that references this table.
Msg1991
Severity16
Group1000–1999

Source: Database Engine events and errors