Oracle 11g Invisible Indexes

CREATE INDEX I_emp_ename ON emp(ename)
TABLESPACE users
STORAGE (INITIAL 10K NEXT 10k PCTINCREASE 50)
INVISIBLE;

ALTER INDEX I_emp_ename INVISIBLE;

ALTER INDEX I_emp_ename VISIBLE;


SELECT INDEX_NAME, VISIBILITY FROM USER_INDEXES
WHERE INDEX_NAME = 'I_EMP_ENAME';

INDEX_NAME VISIBILITY
---------- ----------I_EMP_ENAME VISIBLE