Oracle: wait statisics by block class

This query helps to get information about the wait statistics (in fact, this query is contained in GV_$WAITSTAT)

DECODE (indx,
1,'data block',
2,'sort block',
3,'save undo block',
4,'segment header',
5,'save undo header',
6,'free list',
7,'extent map',
8,'1st level bmb',
9,'2nd level bmb',
10,'3rd level bmb',
11,'bitmap block',
12,'bitmap index block',
13,'file header block',
15,'system undo header',
16,'system undo block',
17,'undo header',
18,'undo block'
), count, time
FROM x$kcbwait
WHERE indx != 0;