Why my index don't update? I have created this index

ORACLE/VIDEO# create index titolo_index
  2  on titolo(titolo)
  3   indextype is ctxsys.context
  4  ONLINE
  5  ;


I do a research

select * from generale where CONTAINS(titolo, '%ragazzi%')&gt;0 order by titolo;

   159|I ragazzi della roma violenta                   |1976   |Drammatico    |1:30    |Vhs       |Italiano


I change from roma to Roma

update titolo set titolo = 'I ragazzi della Roma violenta' where idtitolo = 159;


And it disappear from index!
Why?
Indexing with Oracle Text


  3.3.6.1 CONTEXT Index and DML
  
  A CONTEXT index is not transactional. When you perform inserts,
  updates, or deletes on the base table, you must explicitly synchronize
  the index with CTX_DDL.SYNC_INDEX.