rebuild和rebuild online的区别

SQL> eXPlain plan for

2 alter index test.IND_OBJECT_ID rebuild;

Explained.

SQL> select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT

--------------------------------------------------------------------------------

-------------------------------------------------------------------------

Id Operation Name Rows Bytes Cost

-------------------------------------------------------------------------

0 ALTER INDEX STATEMENT 6235 18705 10

1 INDEX BUILD NON UNIQUE IND_OBJECT_ID

2 SORT CREATE INDEX 6235 18705

3 INDEX FAST FULL SCAN IND_OBJECT_ID 6235 18705

-------------------------------------------------------------------------

Note: cpu costing is off

11 rows selected.

SQL> explain plan for

2 alter index test.IND_OBJECT_ID rebuild online;

Explained.

SQL> select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT

--------------------------------------------------------------------------------

-------------------------------------------------------------------------

Id Operation Name Rows Bytes Cost

-------------------------------------------------------------------------

0 ALTER INDEX STATEMENT 6235 18705 10

1 INDEX BUILD NON UNIQUE IND_OBJECT_ID

2 SORT CREATE INDEX 6235 18705

3 TABLE Access FULL T 6235 18705 10

-------------------------------------------------------------------------

Note: cpu costing is off

11 rows selected.

SQL>

可见rebuild 和rebuild online的扫描方式不同，但都会发生sort.

在rebuild online 时会报错

ORA-08120: Need to create SYS.IND_ONLINE$ table in order to (re)build index

Cause: Alter index Build/Rebuild online require existing of SYS.IND_ONLINE$ table.

Action: User/DBA needs to create sys.ind_online$ before alter the index /rdbms/admin/catcio.sql contains script to create ind_online$.

解决方法就是运行catcio.sql 创建SYS.IND_ONLINE$表

SQL> conn / as sysdba

Connected.

SQL> @D:Oracleora92rdbmsadmincatcio

除了扫描方式不同外，rebuild 会阻塞dml语句而rebuild online则不会。

rebuild online时系统会产生一个SYS_JOURNAL_xxx的IOT类型的系统临时日志表，所有rebuild online时索引的变化都记录在这个表中，当新的索引创建完成后，把这个表的记录维护到新的索引中去，然后drop掉旧的索引，rebuild online就完成了。 Trackback: http://tb.blog.csdn.net/TrackBack.ASPx?PostId=1479533