HWM下被使用了的block佔hwm下所有block的百分比計算！

可以大致看一下hwm下有多少block是free的。[@more@]

SQL> select count(*) from t;

COUNT(*)
----------
126264

SQL> delete from t where object_id<14000;

已刪除96216行。

SQL> commit;

提交完成。

SQL> analyze table t compute statistics;

表已分析。

SQL> select blocks,empty_blocks,num_rows from dba_tables where table_name='T' an
d owner='SYS';

BLOCKS EMPTY_BLOCKS NUM_ROWS
---------- ------------ ----------
1756 36 30048

SQL> select count(distinct dbms_rowid.rowid_block_number(rowid)) from t;

COUNT(DISTINCTDBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID))
---------------------------------------------------
605
SQL> select round(100*605/1756,2) from dual;

ROUND(100*605/1756,2)
---------------------
34.45

SQL>