SQL> INSERT INTO T1 SELECT * FROM T11;

30100005 rows created.

SQL> analyze index T1_INDEX validate structure;

Index analyzed.

SQL> select name,HEIGHT,PCT_USED,DEL_LF_ROWS/LF_ROWS from index_stats;

NAME
--------------------------------------------------
    HEIGHT   PCT_USED DEL_LF_ROWS/LF_ROWS
---------- ---------- -------------------
T1_INDEX
         3        100                   0

这里主要通过几个标准来判断是否需要整理碎片：

1.HEIGHT>=4
2.PCT_USED<50% 3.DEL_ROWS/LF_ROWS>0.2
如果查询到的值符合以上三种情况的任意一种，就说明我们需要进行碎片整理工作了

SQL> delete from T1;

30100005 rows deleted.

SQL> select name,HEIGHT,PCT_USED,DEL_LF_ROWS/LF_ROWS from index_stats;

NAME
--------------------------------------------------
    HEIGHT   PCT_USED DEL_LF_ROWS/LF_ROWS
---------- ---------- -------------------
T1_INDEX
         3        100                   0


SQL> alter index T1_INDEX rebuild online;

Index altered.

SQL> select name,HEIGHT,PCT_USED,DEL_LF_ROWS/LF_ROWS from index_stats;

no rows selected

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