SQL> create table exceptions(row_id rowid,
2 owner varchar2(30),
3 table_name varchar2(30),
4 constraint varchar2(30));

Table created
SQL> create table t1(c1 number);

Table created.

Elapsed: 00:00:03.06
SQL> alter table t1 add constraint cts_t1 unique(c1);

Table altered.

Elapsed: 00:00:00.04
SQL> set timing off;
SQL> insert into t1 values(1);

1 row created.

SQL> insert into t1 values(2);

1 row created.

SQL> commit;

Commit complete.

SQL> alter table t1 disable constraint cts_t1;

Table altered.

SQL> insert into t1 values(1);

1 row created.

SQL> commit;

Commit complete.

SQL> alter table t1 enable constraint cts_t1 exceptions into exceptions;
alter table t1 enable constraint cts_t1 exceptions into exceptions
*
ERROR at line 1:
ORA-02299: cannot validate (TEST.CTS_T1) - duplicate keys found

SQL> select * from t1;

C1
----------
1
2
1

SQL> select * from exceptions;

ROW_ID OWNER TABLE_NAME CONSTRAINT
------------------ ------------------------------ ------------------------------ -------------------
AAAHgPAAKAAAAAiAAA TEST T1 CTS_T1
AAAHgPAAKAAAAAiAAC TEST T1 CTS_T1

SQL> select rowid,c1 from t1;

ROWID C1
------------------ ----------
AAAHgPAAKAAAAAiAAA 1
AAAHgPAAKAAAAAiAAB 2
AAAHgPAAKAAAAAiAAC 1