V$BH视图提供了一个列DIRTY，用于指出BUFFER CACHE中某个数据块是否是DIRTY的，取值为Y或者N。
如下：
> select dirty,count(1) from v$bh group by dirty;
DI COUNT(1)
-- ----------
Y 158
N 1472703
> update test set object_id=object_id;
391898 rows updated.
> commit;
Commit complete.
> select dirty,count(1) from v$bh group by dirty;
DI COUNT(1)
-- ----------
Y 13572
N 1459296
> alter system checkpoint;
System altered.
> select dirty,count(1) from v$bh group by dirty;
DI COUNT(1)
-- ----------
Y 117
N 1472751
>
仅供参考。
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