If you need to find information on the data dictionary concerning constraints, you have only two general views to access to find that information:
DBA_CONS_COLUMNS (ALL_CONS_COLUMNS and USER_CONS_COLUMNS) shows columns affected by each constraint and all the constraints that affect columns. From this view, you can find the constraint name, the table name, the column name, and the position of the column in the constraint (for multicolumn constraints).
DBA_CONSTRAINTS (ALL_CONSTRAINTS and USER_CONSTRAINTS) defines the constraints defined within the database, the constraint type, deletion rule (cascade or not), the deferrable and deferred statuses, and other pertinent information.