[20160302]关于bootstrap$的替换3.txt
--前几天写了关于启动时读取bootstrap$的内容。链接如下：http://blog.itpub.net/267265/viewspace-2016219/
--理论将可以自己建立一个新的bootstrap$替换它。自己测试看看。
1.环境：
--安全起见，先做一个冷备份。
SYS@book> @ &r/ver1
PORT_STRING VERSION BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
create table bootstrap1 as select * from bootstrap$ ;
SYS@book> delete from bootstrap1 where LINE#=59;
1 row deleted.
SYS@book> commit ;
Commit complete.
SYS@book> select object_id,data_object_id,object_name from dba_objects where object_name='BOOTSTRAP1';
OBJECT_ID DATA_OBJECT_ID OBJECT_NAME
---------- -------------- --------------------
91230 91230 BOOTSTRAP1
SYS@book> select owner,segment_name,header_file,header_block from dba_segments where segment_name='BOOTSTRAP1';
OWNER SEGMENT_NAME HEADER_FILE HEADER_BLOCK
------ -------------------- ----------- ------------
SYS BOOTSTRAP1 1 94712
SYS@book> select * from dba_extents where segment_name='BOOTSTRAP1';
OWNER SEGMENT_NAME SEGMENT_TYPE TABLESPACE_NAME EXTENT_ID FILE_ID BLOCK_ID BYTES BLOCKS RELATIVE_FNO
------ -------------------- ------------------ --------------- ---------- ---------- ---------- ---------- ---------- ------------
SYS BOOTSTRAP1 TABLE SYSTEM 0 1 94712 65536 8 1
SYS@book> @ &r/convrdba 1 94712
old 2: TO_CHAR (dbms_utility.make_data_block_address(&1,&2), 'xxxxxxxxxxxxx') rdba16,
new 2: TO_CHAR (dbms_utility.make_data_block_address(1,94712), 'xxxxxxxxxxxxx') rdba16,
old 3: dbms_utility.make_data_block_address(&&1,&&2) rdba
new 3: dbms_utility.make_data_block_address(1,94712) rdba
RDBA16 RDBA
-------------- ----------
4171f8 4289016
BBED> set dba 1,94712
DBA 0x004171f8 (4289016 1,94712)
SYS@book> @ &r/bbvi 1 1
BVI_COMMAND
-----------------------------------------------------
bvi -b 8192 -s 8192 /mnt/ramdisk/book/system01.dbf
SYS@book> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
2.修改：
$ bvi -b 8192 -s 8192 /mnt/ramdisk/book/system01.dbf
--反转一下就是修改偏移量96处为 f8714100
BBED> set dba 1,1
DBA 0x00400001 (4194305 1,1)
BBED> p kcvfhrdb
ub4 kcvfhrdb @96 0x004171f8
BBED> sum
Check value for File 1, Block 1:
current = 0x1f28, required = 0x6cd9
BBED> sum apply
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
Check value for File 1, Block 1:
current = 0x6cd9, required = 0x6cd9
3.启动测试：
SYS@book> startup
ORACLE instance started.
Total System Global Area 634679296 bytes
Fixed Size 2255912 bytes
Variable Size 264242136 bytes
Database Buffers 360710144 bytes
Redo Buffers 7471104 bytes
Database mounted.
Database opened.
--OK!但是这样存在一个问题：
SYS@book> select rowid,a.* from bootstrap1 a where line#=2;
ROWID LINE# OBJ# SQL_TEXT
------------------ ---------- ---------- ------------------------------------------------------------
AAAWReAABAAAXH7AAG 2 2 CREATE CLUSTER C_OBJ#("OBJ#" NUMBER) PCTFREE 5 PCTUSED 40 IN
ITRANS 2 MAXTRANS 255 STORAGE ( INITIAL 136K NEXT 200K MINE
XTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 2 EXTENTS
(FILE 1 BLOCK 144)) SIZE 800
SYS@book> select rowid,a.* from bootstrap$ a where line#=2;
ROWID LINE# OBJ# SQL_TEXT
------------------ ---------- ---------- ------------------------------------------------------------
AAAWReAABAAAXH7AAG 2 2 CREATE CLUSTER C_OBJ#("OBJ#" NUMBER) PCTFREE 5 PCTUSED 40 IN
ITRANS 2 MAXTRANS 255 STORAGE ( INITIAL 136K NEXT 200K MINE
XTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 2 EXTENTS
(FILE 1 BLOCK 144)) SIZE 800
SYS@book> @ &r/rowid AAAWReAABAAAXH7AAG
OBJECT FILE BLOCK ROW DBA TEXT
---------- ---------- ---------- ---------- -------------------- ----------------------------------------
91230 1 94715 6 1,94715 alter system dump datafile 1 block 94715
--可以发现现在bootstrap1与bootstrap$指向相同的位置。而实际的情况是：
SYS@book> select owner,segment_name,header_file,header_block from dba_segments where segment_name='BOOTSTRAP1';
OWNER SEGMENT_NAME HEADER_FILE HEADER_BLOCK
------ -------------------- ----------- ------------
SYS BOOTSTRAP1 1 94712
SYS@book> select owner,segment_name,header_file,header_block from dba_segments where segment_name='BOOTSTRAP$';
OWNER SEGMENT_NAME HEADER_FILE HEADER_BLOCK
------ -------------------- ----------- ------------
SYS BOOTSTRAP$ 1 520
4.继续测试：
--实际上现在bootstrap$实际上读的是HEADER_BLOCK=94712,也就是BOOTSTRAP1.不建议做这样的修改，仅仅为了学习。
--千万不要在生产系统做这样的测试。
SYS@book> alter system flush shared_pool;
System altered.
SYS@book> select rowid,a.* from bootstrap$ a where line#=2;
ROWID LINE# OBJ# SQL_TEXT
------------------ ---------- ---------- ------------------------------------------------------------
AAAWReAABAAAXH7AAG 2 2 CREATE CLUSTER C_OBJ#("OBJ#" NUMBER) PCTFREE 5 PCTUSED 40 IN
ITRANS 2 MAXTRANS 255 STORAGE ( INITIAL 136K NEXT 200K MINE
XTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 2 EXTENTS
(FILE 1 BLOCK 144)) SIZE 800
--感觉有点怪怪的。最好的方式是改名看看。
SYS@book> rename bootstrap$ to bootstrapx;
rename bootstrap$ to bootstrapx
*
ERROR at line 1:
ORA-00701: object necessary for warmstarting database cannot be altered
$ oerr ora 701
00701, 00000, "object necessary for warmstarting database cannot be altered"
// *Cause: Attempt to alter or drop a database object (table, cluster, or
// index) which are needed for warmstarting the database.
// *Action: None.
--实际上可以参考链接http://www.xifenfei.com/5021.html，使用exec DBMS_DDL_INTERNAL.SWAP_BOOTSTRAP('BOOTSTRAP1').而不是手工操作，
--大家可以参考链接再测试，不再测试。
SYS@book> startup upgrade;
ORACLE instance started.
Total System Global Area 634679296 bytes
Fixed Size 2255912 bytes
Variable Size 264242136 bytes
Database Buffers 360710144 bytes
Redo Buffers 7471104 bytes
Database mounted.
Database opened.
SYS@book> rename bootstrap$ to bootstrapx;
rename bootstrap$ to bootstrapx
*
ERROR at line 1:
ORA-00701: object necessary for warmstarting database cannot be altered
SYS@book> drop table bootstrap$ ;
drop table bootstrap$
*
ERROR at line 1:
ORA-00701: object necessary for warmstarting database cannot be altered
--我的这个版本根本不能改名与删除。也许要通过直接修改内部表obj$，对换名字。
SYS@book> select obj#,owner#,name,namespace from obj$ where obj# in (59,91230);
OBJ# OWNER# NAME NAMESPACE
---------- ---------- -------------------- ----------
59 0 BOOTSTRAP$ 1
91230 0 BOOTSTRAP1 1
SYS@book> update obj$ set name='BOOTSTRAPX' where obj#=59;
1 row updated.
SYS@book> update obj$ set name='BOOTSTRAP$' where obj#=91230;
1 row updated.
SYS@book> select obj#,owner#,name,namespace from obj$ where obj# in (59,91230);
OBJ# OWNER# NAME NAMESPACE
---------- ---------- -------------------- ----------
59 0 BOOTSTRAPX 1
91230 0 BOOTSTRAP$ 1
SYS@book> commit ;
Commit complete.
--重新启动再测试：
SYS@book> startup
ORACLE instance started.
Total System Global Area 634679296 bytes
Fixed Size 2255912 bytes
Variable Size 264242136 bytes
Database Buffers 360710144 bytes
Redo Buffers 7471104 bytes
Database mounted.
Database opened.
--OK!
SYS@book> select rowid,a.* from bootstrap$ a where line#=2;
ROWID LINE# OBJ# SQL_TEXT
------------------ ---------- ---------- ------------------------------------------------------------
AAAWReAABAAAXH7AAG 2 2 CREATE CLUSTER C_OBJ#("OBJ#" NUMBER) PCTFREE 5 PCTUSED 40 IN
ITRANS 2 MAXTRANS 255 STORAGE ( INITIAL 136K NEXT 200K MINE
XTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 2 EXTENTS
(FILE 1 BLOCK 144)) SIZE 800
SYS@book> select rowid,a.* from bootstrapx a where line#=2;
ROWID LINE# OBJ# SQL_TEXT
------------------ ---------- ---------- ------------------------------------------------------------
AAAAA7AABAAAAILAAG 2 2 CREATE CLUSTER C_OBJ#("OBJ#" NUMBER) PCTFREE 5 PCTUSED 40 IN
ITRANS 2 MAXTRANS 255 STORAGE ( INITIAL 136K NEXT 200K MINE
XTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 2 EXTENTS
(FILE 1 BLOCK 144)) SIZE 800
--rowid 不一样了。
SYS@book> select owner,segment_name,header_file,header_block from dba_segments where segment_name='BOOTSTRAPX';
OWNER SEGMENT_NAME HEADER_FILE HEADER_BLOCK
------ -------------------- ----------- ------------
SYS BOOTSTRAPX 1 520
SYS@book> select owner,segment_name,header_file,header_block from dba_segments where segment_name='BOOTSTRAP$';
OWNER SEGMENT_NAME HEADER_FILE HEADER_BLOCK
------ -------------------- ----------- ------------
SYS BOOTSTRAP$ 1 94712
总结：
1.实际上测试测试仅仅加强理解，不要在生产系统做这样的测试!!!
2.而且如果出现损坏坏块，仅仅损坏这个区域的概率很小，要破坏也是一片区域。另外其他的区域如果破坏，你可以发现
CREATE CLUSTER C_OBJ# 建立在FILE 1 BLOCK 144，如果损坏，数据库也无法启动。