I have a test schema (NCL) with two tablespaces WIZDATA containing tables of test schema and WIZINDX for indexes
Now these tablespaces are no longer required

SQL> drop tablespace wizdata including contents and datafiles;
drop tablespace wizdata including contents and datafiles
*
ERROR at line 1:
ORA-02449: unique/primary keys in table referenced by foreign keys

SQL> drop tablespace wizdata including contents;
drop tablespace wizdata including contents
*
ERROR at line 1:
ORA-02449: unique/primary keys in table referenced by foreign keys


SQL> drop tablespace wizindx including contents and datafiles;
drop tablespace wizindx including contents and datafiles
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-02429: cannot drop index used for enforcement of unique/primary key

SQL> drop user ncl cascade;

User dropped.

SQL> drop tablespace wizdata including contents and datafiles;

Tablespace dropped.

SQL> drop tablespace wizindx including contents and datafiles;

Tablespace dropped.

Now both of tablespaces have been droped after droping the schema NCL

This is quite confusing for me
Can anybody had encountered this problem?