ORA-00701 warmstarting对象的另类解决方法

有朋友在ITPUB问到一个问题，如何resize一个SYSTEM表空间。
从常规来说，如果我们希望resize一个文件，这个文件能够resize的部分必然是没有数据，未被使用的，也就是说，我们需要找到一个文件最高的Extent号，这个Extent之外的空间是可以被resize的,以下一个查询可以帮我们找到一个文件最末端的对象:

col segment_name for a30
col owner for a10
SELECT *
  FROM (SELECT   owner, segment_name,segment_type,block_id, blocks
            FROM dba_extents
           WHERE tablespace_name = 'SYSTEM' and file_id='&fileid'
        ORDER BY block_id DESC)
WHERE ROWNUM < 11;

看一下我的一个数据库:

SQL> col segment_name for a30
SQL> col owner for a10
SQL> SELECT *
  2    FROM (SELECT   owner, segment_name,segment_type,block_id, blocks
  3              FROM dba_extents
  4             WHERE tablespace_name = 'SYSTEM' and file_id='&fileid'
  5          ORDER BY block_id DESC)
  6  WHERE ROWNUM < 11;
Enter value for fileid: 1
old   4:            WHERE tablespace_name = 'SYSTEM' and file_id='&fileid'
new   4:            WHERE tablespace_name = 'SYSTEM' and file_id='1'

OWNER      SEGMENT_NAME                   SEGMENT_TYPE         BLOCK_ID     BLOCKS
---------- ------------------------------ ------------------ ---------- ----------
SYS        EYGLE_IP                       TABLE                   25609        128
SYS        EYGLE_IP                       TABLE                   25481        128
SYS        EYGLE_IP                       TABLE                   25353        128
SYS        I_H_OBJ#_COL#                  INDEX                   25305          8
SYS        TEST                           TABLE                   25297          8
SYS        I_TEST                         INDEX                   25289          8
SYS        TEST                           TABLE                   25281          8
SYS        T                              TABLE                   25273          8
SYS        EYGLE_IP                       TABLE                   25265          8
SYS        EYGLE_IP                       TABLE                   25257          8

10 rows selected.

我们注意到高水位上有些索引是可以通过rebuild来改变其位置的，但是在正常模式下，Oracle不允许rebuild这些索引:

SQL> alter index I_H_OBJ#_COL# rebuild;
alter index I_H_OBJ#_COL# rebuild
*
ERROR at line 1:
ORA-00701: object necessary for warmstarting database cannot be altered

有两种方式可以使得这些对象允许被重建:
1.通过migrate模式

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup migrate;
ORACLE instance started.
Total System Global Area 139531744 bytes
Fixed Size 452064 bytes
Variable Size 121634816 bytes
Database Buffers 16777216 bytes
Redo Buffers 667648 bytes
Database mounted.
Database opened.
SQL> alter index I_H_OBJ#_COL# rebuild;
Index altered.
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 139531744 bytes
Fixed Size 452064 bytes
Variable Size 121634816 bytes
Database Buffers 16777216 bytes
Redo Buffers 667648 bytes
Database mounted.
Database opened.

2.通过一个内部事件

SQL> alter system set event='38003 trace name context forever, level 10' scope=spfile;
System altered.
SQL> startup force;
ORACLE instance started.
Total System Global Area 139531744 bytes
Fixed Size 452064 bytes
Variable Size 121634816 bytes
Database Buffers 16777216 bytes
Redo Buffers 667648 bytes
Database mounted.
Database opened.
SQL> alter index i_h_obj#_col# rebuild;
Index altered.

38003事件的作用是:CBO Disable column stats for the dictionary objects in recursive SQL
也就是说可以将部分对象从启动的bootstrap$需要里剥离出来，从而可以被在线rebuild.
这个事件能够影响的对象很有限，这类操作也是极其危险的，所以不在这里详细列出。
-The End-