Oracle - 坏块修复
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一、概述
本文将介绍如何模拟坏块，以及出现坏块该如何修复。实验分为以下几个步骤。
1. 表出现坏块
2. 索引出现坏块
二、环境准备
本实验都是在oracle 11G归档模式下进行。
1. 准备相关表
create tablespace tbs01 datafile ‘/u01/app/oracle/oradata/orcltest/tbs01.dbf‘ size 100m;
create table scott.t01 tablespace tbs01 as select * from dba_objects where rownum<=100;
create index scott.idx_t01 on scott.t01(object_id) tablespace tbs01;
select rowid, dbms_rowid.rowid_relative_fno(rowid) file_id, dbms_rowid.rowid_block_number(rowid) block_id from scott.t01;
ROWID FILE_ID BLOCK_ID ------------------ ---------- ---------- AAAVpMAAGAAAACDAAA 6 131 AAAVpMAAGAAAACDAAB 6 131 AAAVpMAAGAAAACDAAC 6 131 AAAVpMAAGAAAACDAAD 6 131 AAAVpMAAGAAAACDAAE 6 131 AAAVpMAAGAAAACDAAF 6 131 AAAVpMAAGAAAACDAAG 6 131 ...
select segment_name, segment_type, file_id, block_id, blocks from dba_extents where segment_name=‘IDX_T01‘;
SEGMENT_NAME SEGMENT_TYPE FILE_ID BLOCK_ID BLOCKS --------------- ------------------ ---------- ---------- ---------- IDX_T01 INDEX 6 136 8
2. 全库备份
RMAN> backup database; // 全库备份
RMAN> list backup; // 查看备份
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
19 Full 1.08G DISK 00:01:59 12-MAR-20
BP Key: 19 Status: AVAILABLE Compressed: NO Tag: TAG20200312T150629
Piece Name: /home/oracle/backupdir/ORCLTEST_2750922031_40_1_20200312_1034867190.bkp
List of Datafiles in backup set 19
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
1 Full 1148218 12-MAR-20 /u01/app/oracle/oradata/orcltest/system01.dbf
2 Full 1148218 12-MAR-20 /u01/app/oracle/oradata/orcltest/sysaux01.dbf
3 Full 1148218 12-MAR-20 /u01/app/oracle/oradata/orcltest/undotbs01.dbf
4 Full 1148218 12-MAR-20 /u01/app/oracle/oradata/orcltest/users01.dbf
5 Full 1148218 12-MAR-20 /u01/app/oracle/oradata/orcltest/example01.dbf
6 Full 1148218 12-MAR-20 /u01/app/oracle/oradata/orcltest/tbs01.dbf三、正式实验
1. 表出现坏块
1.1 模拟坏块
RMAN> blockrecover datafile 6 block 131 clear; // 将131数据块清空，即相当于产生了坏块
SQL> select * from scott.t01; // 对表进行查询
select * from scott.t01
*
ERROR at line 1:
ORA-01578: ORACLE data block corrupted (file # 6, block # 131)
ORA-01110: data file 6: ‘/u01/app/oracle/oradata/orcltest/tbs01.dbf‘1.2 检测坏块
检测坏块可以使用以下两种方式
a. 使用rman检测坏块
RMAN> backup check logical validate datafile 6;
List of Datafiles ================= File Status Marked Corrupt Empty Blocks Blocks Examined High SCN ---- ------ -------------- ------------ --------------- ---------- 6 FAILED 0 12656 12800 1234072 File Name: /u01/app/oracle/oradata/orcltest/tbs01.dbf Block Type Blocks Failing Blocks Processed ---------- -------------- ---------------- Data 1 2 Index 0 3 Other 0 139 validate found one or more corrupt blocks
上面rman检测到的坏块具体信息可以通过v$database_block_corruption查看
b. 使用oracle安装时自带的dbv工具
[oracle@orasingle ~]$ dbv file=‘/u01/app/oracle/oradata/orcltest/tbs01.dbf‘
Total Pages Examined : 12800 Total Pages Processed (Data) : 1 Total Pages Failing (Data) : 0 Total Pages Processed (Index): 3 Total Pages Failing (Index): 0 Total Pages Processed (Other): 139 Total Pages Processed (Seg) : 0 Total Pages Failing (Seg) : 0 Total Pages Empty : 12656 Total Pages Marked Corrupt : 1 Total Pages Influx : 1 Total Pages Encrypted : 0 Highest block SCN : 1234072 (0.1234072)
1.3 坏块修复
RMAN> backup check logical validate datafile 6; // 检测数据文件的坏块
RMAN> blockrecover corruption list; // 自动修复检测出的坏块，该命令执行成功的前提是有完整的rman备份
SQL> select * from scott.t01; // 再查询就没有错误了
2. 索引出现坏块
查看下面sql的执行计划
SQL> select * from scott.t01 where object_id=100;
SQL> select * from table(dbms_xplan.display_cursor(null,null,‘TYPICAL PEEKED_BINDS‘));
--------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 2 (100)| | | 1 | TABLE ACCESS BY INDEX ROWID| T01 | 1 | 207 | 2 (0)| 00:00:01 | |* 2 | INDEX RANGE SCAN | IDX_T01 | 1 | | 1 (0)| 00:00:01 | ---------------------------------------------------------------------------------------
2.1 模拟坏块
RMAN> blockrecover datafile 6 block 139 clear; // 将139索引块清空，即相当于索引产生了坏块
可能大家会有疑惑，该索引的块的block_id是136，你为什么要清空139呢？这就涉及到段的管理方式了，136-138这三个块依次是一级位图块，二级位图块，段头。真正存放数据的是从139开始。可以将块dump出来看看块的类型。
SQL> select * from scott.t01 where object_id=100; // 再来查询该sql
select * from scott.t01 where object_id=100 * ERROR at line 1: ORA-01578: ORACLE data block corrupted (file # 6, block # 139) ORA-01110: data file 6: ‘/u01/app/oracle/oradata/orcltest/tbs01.dbf‘
在这里我们可以看到，这里的报错与前面表上有坏块的报错一模一样，因此当我们查询一张表出现这类报错的时候，可能并不是表有坏块，而可能是这张表上的索引有坏块。
2.2 检查坏块
RMAN> backup check logical validate datafile 6;
List of Datafiles ================= File Status Marked Corrupt Empty Blocks Blocks Examined High SCN ---- ------ -------------- ------------ --------------- ---------- 6 FAILED 0 12657 12800 1158959 File Name: /u01/app/oracle/oradata/orcltest/tbs01.dbf Block Type Blocks Failing Blocks Processed ---------- -------------- ---------------- Data 0 1 Index 1 3 Other 0 139 validate found one or more corrupt blocks
同样也可以通过下面的sql确定坏块的段类型。
select owner, segment_name, segment_type from dba_extents where 139 between block_id and block_id+blocks-1 and file_id=6;
2.3 修复坏块
索引的坏块修复有两种方式，第一种就是跟表一样，直接修复数据文件
RMAN> backup check logical validate datafile 6; // 检测数据文件的坏块
RMAN> blockrecover corruption list; // 自动修复检测出的坏块
第二种方式就是将索引直接删了重建，原理就是如果索引被删除了，这个段就会被系统回收，该段上所有的块都会被初始化，也就不存在什么坏块了。
select dbms_metadata.get_ddl(‘INDEX‘, ‘IDX_T01‘, ‘SCOTT‘) from dual; // 通过该sql查索引的创建信息
drop index scott.idx_t01; // 删除索引
CREATE INDEX "SCOTT"."IDX_T01" ON "SCOTT"."T01" ("OBJECT_ID") TABLESPACE "TBS01" online; // 创建索引
2.4 试试rebuild online
可能你会问，为什么索引删了重建，直接rebuild不更好吗？那么我们再试试索引有坏块了，rebuild是个什么效果
RMAN> blockrecover datafile 6 block 139 clear;
RMAN> backup check logical validate datafile 6;
List of Datafiles ================= File Status Marked Corrupt Empty Blocks Blocks Examined High SCN ---- ------ -------------- ------------ --------------- ---------- 6 FAILED 0 12656 12800 1234071 File Name: /u01/app/oracle/oradata/orcltest/tbs01.dbf Block Type Blocks Failing Blocks Processed ---------- -------------- ---------------- Data 0 2 Index 1 3 Other 0 139
使用rebuild命令重建索引
alter index scott.idx_t01 rebuild online;
RMAN> backup check logical validate datafile 6; // 可以看到坏块依然存在
List of Datafiles ================= File Status Marked Corrupt Empty Blocks Blocks Examined High SCN ---- ------ -------------- ------------ --------------- ---------- 6 FAILED 0 12656 12800 1237004 File Name: /u01/app/oracle/oradata/orcltest/tbs01.dbf Block Type Blocks Failing Blocks Processed ---------- -------------- ---------------- Data 0 2 Index 1 3 Other 0 139
select * from scott.t01 where object_id=100; // 查询没有问题，索引也有效
select * from table(dbms_xplan.display_cursor(null,null,‘TYPICAL PEEKED_BINDS‘));
--------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 2 (100)| | | 1 | TABLE ACCESS BY INDEX ROWID| T01 | 1 | 207 | 2 (0)| 00:00:01 | |* 2 | INDEX RANGE SCAN | IDX_T01 | 1 | | 1 (0)| 00:00:01 | ---------------------------------------------------------------------------------------
所以，如果是索引的坏块，不建议使用rebuild online，因为它虽然让索引能够正常使用，但是坏块依然存在。
四、总结
1. 坏块修复的前提是要有完整的备份，所以一定得为生产环境指定备份策略
2. 表的坏块恢复直接使用rman
3. 索引的坏块恢复可以使用rman，也可通过删除索引再重建的方式修复
如果该主库有dg，那么主库有坏块又该如何修复，dg有坏块又该如何修复，请看“dg坏块修复(二)”
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