ORA-02449: unique/primary keys in table referenced by foreign keys

SQL> DROP TABLE CDR;
DROP TABLE CDR;
*
ERROR at line 1:
ORA-02449: unique/primary keys in table referenced by foreign keys

SQL> SELECT  TABLE_NAME,CONSTRAINT_NAME,CONSTRAINT_TYPE,R_CONSTRAINT_NAME,STATUS
     FROM    DBA_CONSTRAINTS
     WHERE   OWNER = 'TEST'
     AND     CONSTRAINT_TYPE='R'
     AND     R_CONSTRAINT_NAME IN (SELECT CONSTRAINT_NAME FROM DBA_CONSTRAINTS WHERE TABLE_NAME='CDR');

TABLE_NAME     CONSTRAINT_NAME  C R_CONSTRAINT_NAME   STATUS
-------------- ---------------- - ------------------- --------
TRANSACTION    FK_TRANSACTION   R SYS_C0096900        ENABLED

SQL>  alter table TRANSACTION disable constraint FK_TRANSACTION;

Table altered.

SQL> DROP TABLE CDR;
DROP TABLE CDR;
*
ERROR at line 1:
ORA-02449: unique/primary keys in table referenced by foreign keys

SQL>  alter table TRANSACTION drop constraint FK_TRANSACTION;

Table altered.

SQL> DROP TABLE CDR;

Table dropped.

SQL> DROP TABLE CDR CASCADE CONSTRAINTS;

Table dropped.