[20180306]数据块检查和.txt
--//如果数据块检查和不对,数据库无法读取相应块,会报错.
--//检查和位于块偏移16字节处.
ub1 flg_kcbh @15
ub2 chkval_kcbh @16
--//实际上如果设置flg_kcbh,chkval_kcbh=0,一般数据块是可以跳过的.测试看看.
--//注意:要关闭dg,不然会自动修复.
1.环境:
SCOTT@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
SCOTT@book> create table deptx tablespace tea as select * from dept;
Table created.
SCOTT@book> select rowid,deptx.* from deptx;
ROWID DEPTNO DNAME LOC
------------------ ---------- -------------- -------------
AAAWGWAAGAAAACBAAA 10 ACCOUNTING NEW YORK
AAAWGWAAGAAAACBAAB 20 RESEARCH DALLAS
AAAWGWAAGAAAACBAAC 30 SALES CHICAGO
AAAWGWAAGAAAACBAAD 40 OPERATIONS BOSTON
SCOTT@book> @ &r/rowid AAAWGWAAGAAAACBAAA
OBJECT FILE BLOCK ROW ROWID_DBA DBA TEXT
---------- ---------- ---------- ---------- -------------------- -------------------- ----------------------------------------
90518 6 129 0 0x1800081 6,129 alter system dump datafile 6 block 129 ;
SCOTT@book> alter system checkpoint ;
System altered.
SCOTT@book> alter system flush buffer_cache;
System altered.
2.使用bbed修改块6,129.
SCOTT@book> @ &r/bbvi 6 129
BVI_COMMAND
----------------------------------------------------------------------------------------------------
bvi -b 1056768 -s 8192 /mnt/ramdisk/book/tea01.dbf
--//使用bvi修改ACCOUNTING为A12OUNTING.
BBED> set dba 6,129
DBA 0x01800081 (25165953 6,129)
BBED> x /rncc *kdbr[0]
rowdata[66] @8162
-----------
flag@8162: 0x2c (KDRHFL, KDRHFF, KDRHFH)
lock@8163: 0x00
cols@8164: 3
col 0[2] @8165: 10
col 1[10] @8168: A12OUNTING
col 2[8] @8179: NEW YORK
BBED> sum
Check value for File 6, Block 129:
current = 0x49c5, required = 0x38b7
--//可以发现现在已经不一致.
SCOTT@book> select rowid,deptx.* from deptx;
select rowid,deptx.* from deptx
*
ERROR at line 1:
ORA-01578: ORACLE data block corrupted (file # 6, block # 129)
ORA-01110: data file 6: '/mnt/ramdisk/book/tea01.dbf'
--//报ORA-01578错误.
3.清除flg_kcbh,chkval_kcbh看看.
SCOTT@book> alter system flush buffer_cache;
System altered.
BBED> assign kcbh.chkval_kcbh=0x0
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
ub2 chkval_kcbh @16 0x0000
BBED> assign kcbh.flg_kcbh=0x0
ub1 flg_kcbh @15 0x00 (NONE)
BBED> sum
Check value for File 6, Block 129:
current = 0x0000, required = 0x0000
--//这样就ok了.
SCOTT@book> select rowid,deptx.* from deptx;
ROWID DEPTNO DNAME LOC
------------------ ---------- -------------- -------------
AAAWGWAAGAAAACBAAA 10 A12OUNTING NEW YORK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
AAAWGWAAGAAAACBAAB 20 RESEARCH DALLAS
AAAWGWAAGAAAACBAAC 30 SALES CHICAGO
AAAWGWAAGAAAACBAAD 40 OPERATIONS BOSTON
--//注意看下划线,以后没有bbed,对于一般的数据块可以直接设置块偏移量15,16,17字节为0x0,就ok了.
--//但是对系统表空间是无效的(没测试).缺省数据库的参数_db_always_check_system_ts=true.
SYS@book> @ &r/hide _db_always_check_system_ts
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE
-------------------------- ------------------------------------------------------------- ------------- ------------- ------------
_db_always_check_system_ts Always perform block check and checksum for System tablespace TRUE TRUE TRUE
