INDEXES CREATION, ENABLE, DISABLE, UNUSABLE & REBUILD ONLINE..

CREATE TABLE A(id NUMBER,NAME VARCHAR2(33));

insert into a VALUES (1,'RAVI');
insert into a VALUES(2,'SINDHU');
insert into a VALUES(3,'RESHWANTH');
insert into a VALUES(4,'MANJIRA');
commit;

create index id_indx on a(id);

DISABLE INDEXES:
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alter index id_indx unusable;

ENABLE INDEXES:
-----------------
alter index id_indx rebuild online;

FUNCTION BASED INDEXES ENBLING N DISABLING:
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create index a_name on a (upper(name));

alter index a_name disable;

alter index a_name enable;