[20190918]shrink space与ORA-08102错误.txt
1.环境:
SCOTT@test01p> @ ver1
PORT_STRING VERSION BANNER CON_ID
------------------------------ -------------- -------------------------------------------------------------------------------- ----------
IBMPC/WIN_NT64-9.1.0 12.2.0.1.0 Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production 0
2.再现ORA-08102错误:
SCOTT@test01p> create table t(x int, pad varchar2(100)) enable row movement;
Table created.
SCOTT@test01p> insert /*+ append*/ into t select level, lpad('x', 100, 'x') from dual connect by level<=1e4;
10000 rows created.
SCOTT@test01p> alter table t add y int default 10 not null;
Table altered.
SCOTT@test01p> create index i_t_xy on t(x,y);
Index created.
SCOTT@test01p> delete t where x<=5000;
5000 rows deleted.
SCOTT@test01p> commit ;
Commit complete.
SCOTT@test01p> alter table t shrink space;
alter table t shrink space
*
ERROR at line 1:
ORA-08102: index key not found, obj# 27979, file 11, block 2445 (2)
SCOTT@test01p> host oerr ora 8102
08102, 00000, "index key not found, obj# %s, file %s, block %s (%s)"
// *Cause: Internal error: possible inconsistency in index
// *Action: Send trace file to your customer support representative, along
// with information on reproducing the error
3.10046跟踪看看.
SCOTT@test01p> alter session set events '10046 level 12';
Session altered.
SCOTT@test01p> alter table t shrink space;
alter table t shrink space
*
ERROR at line 1:
ORA-08102: index key not found, obj# 27979, file 11, block 2445 (2)
SCOTT@test01p> alter session set events '10046 off';
Session altered.
--//检查转储发现:
oer 8102.2 - obj# 27979, rdba: 0x02c0098d(afn 11, blk# 2445)
kdk key 8102.2:
ncol: 3, len: 12
key: (12): 03 c2 64 31 ff 06 02 c0 1d a5 00 00
mask: (2048):
--//通过bbed观察看看.
--//03 c2 64 31 ,03表示长度.后面3位表示oracle数字.
SCOTT@test01p> @ conv_n c26431
N20
----------
9948
BBED> set dba 11,2446
DBA 0x02c0098e (46139790 11,2446)
--//注:windows下bbed,无法识别10g以上版本的os头,block存在+1的偏移.
BBED> map
File: D:APPORACLEORADATATESTTEST01PUSERS01.DBF (11)
Block: 2446 Dba:0x02c0098e
------------------------------------------------------------
KTB Data Block (Index Leaf)
struct kcbh, 20 bytes @0
struct ktbbh, 72 bytes @20
struct kdxle, 32 bytes @100
b2 kd_off[399] @132
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
ub1 freespace[822] @930
ub1 rowdata[6380] @1752
ub4 tailchk @8188
BBED> x /rnnx *kd_off[3]
rowdata[6352] @8104
-------------
flag@8104: 0x00 (NONE)
lock@8105: 0x00
data key:
col 0[3] @8107: 9583
col 1[2] @8111: 10
col 2[6] @8114: 0x02 0xc0 0x1d 0x9f 0x00 0x19
--//9948-9583+3 = 368
BBED> x /rnnx *kd_off[368]
rowdata[516] @2268
------------
flag@2268: 0x00 (NONE)
lock@2269: 0x00
data key:
col 0[3] @2271: 9948
col 1[2] @2275: 10
col 2[6] @2278: 0x02 0xc0 0x1d 0xa5 0x00 0x00
BBED> x /rxxx *kd_off[368]
rowdata[516] @2268
------------
flag@2268: 0x00 (NONE)
lock@2269: 0x00
data key:
col 0[3] @2271: 0xc2 0x64 0x31
col 1[2] @2275: 0xc1 0x0b
col 2[6] @2278: 0x02 0xc0 0x1d 0xa5 0x00 0x00
--//可以看出原来的key是 03 c2 64 31 02 c1 0b 06 02 c0 1d a5 00 00
--//而shrink space后,索引的键值发生了变化,变为如下:
--//key: (12): 03 c2 64 31 ff 06 02 c0 1d a5 00 00
--//0xff表示NULL,参考链接:http://blog.itpub.net/267265/viewspace-2120439/=>[20160619]NULL在数据库的存储.txt
--//也就是索引的第2字段oracle认为是NULL,也就是遇到这样的情况shrink space时.oracle错误的认为Y=null,
--//因为这样的情况Y=10的值并没有保存在数据块中,而是放在sys.ecol$中.
SCOTT@test01p> SELECT * FROM sys.ecol$ WHERE tabobj# IN (SELECT DATA_OBJECT_ID FROM dba_objects WHERE owner = USER AND object_name = 'T');
TABOBJ# COLNUM BINARYDEFVAL GUARD_ID
---------- ---------- ------------------------------ ----------
27978 3 C10B
--//c10b对应number类型是数字10.
--//对于这样的情况如果要降低HWM,仅仅ctas建立表以及索引.
--//如果增加字段时写入数据块中,应该不会出现这样的情况.看了一下隐含参数,应该是_add_col_optim_enabled.
SYS@test> @ hide _add_col_optim_enabled
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ISSES ISSYS_MOD
---------------------- ---------------------------------- ------------- ------------- ------------ ----- ---------
_add_col_optim_enabled Allows new add column optimization TRUE TRUE TRUE TRUE IMMEDIATE
SCOTT@test01p> alter session set "_add_col_optim_enabled"=false;
Session altered.
create table t1(x int, pad varchar2(100)) enable row movement;
insert /*+ append*/ into t1 select level, lpad('x', 100, 'x') from dual connect by level<=1e4;
alter table t1 add y int default 10 not null;
create index i_t1_xy on t1(x,y);
delete t1 where x<=5000;
commit ;
alter table t1 shrink space;
SCOTT@test01p> alter table t1 shrink space;
Table altered.
--//当然这样增加字段就很慢!!
总结:
如果要做shrink space,最好先检查看看是否曾经这样增加过新字段.