redo丢失的各种情况处理

测试环境oracle版本：19.3（NOARCHIVELOG MODE）

场景1：被删的redo组有冗余（无论redo的状态如何）

1、构造故障场景

（1）查看当前redo配置

set lines 400 pages 9999

col MEMBER for a50

select v1.status, v1.group#, v1.bytes/1024/1024/1024,member,thread# ,sequence#, to_char(first_change#),to_char(NEXT_CHANGE#) from v$log v1, v$logfile v2 where v1.group# = v2.group# order by thread#, v1.group#, member ;

（2）构造冗余的redo组

alter database drop logfile group 8;

alter database add logfile thread 1 group 8 ('/oradata/CC/redo08_1.log','/oradata/CC/redo08_2.log') size 2g ;

（3）关闭归档

shutdown immediate

startup mount

alter database noarchivelog;

alter database open;

（4）切归档，将冗余的log组设为current

alter system switch logfile;

（5）删除冗余的member

rm -f /oradata/CC/redo08_2.log

（6）查看alert日志

查看alert日志中lg00的trace日志，报错如下

2、解决思路

redo组若有冗余不影响数据库的写入操作，但是alert会有报错，可以把缺失的member从数据库中移除，然后重新添加即可

3、解决步骤

（1）切归档，将缺少redo member的组切换非current

alter system switch logfile;

CURRENT状态会导致drop不成功

（2）执行drop缺失的member

alter database drop logfile member '/oradata/CC/redo08_2.log'

（3）重新添加member

alter database add logfile member '/oradata/CC/redo08_2.log' to group 8;

（4）将current redo切到此磁盘组，alert日志不再报错

4、风险评估

由于redo member有冗余，即使丢失一个member也不会影响业务，无大的风险

场景2：被删的redo组无冗余（INACTIVE的redo组）

1、构造故障场景

（1）查看当前redo配置

set lines 400 pages 9999

col MEMBER for a50

select v1.status, v1.group#, v1.bytes/1024/1024/1024,member,thread# ,sequence#, to_char(first_change#),to_char(NEXT_CHANGE#) from v$log v1, v$logfile v2 where v1.group# = v2.group# order by thread#, v1.group#, member ;

（2）删除INACTIVE的redo组对应的redo文件

rm -f /oradata/CC/redo01.log

（3）切归档直到被删的redo组为current

alter system switch logfile;

此时会导致数据库崩溃

2、解决思路

分为两种情况：

情况1：

删除INACTIVE的redo后立马处理，执行alter database clear unarchived logfile group 1即可恢复

情况2：

删除INACTIVE的redo后没有即时干预，一旦被切为CURRENT会导致实例崩溃，此时就要按照CURRENT REDO被删的场景来解决

3、解决步骤

情况1：

alter database clear unarchived logfile group 1;

重新生成redo，alert日志报错如下（但是成功将redo01生成）

且alert日志不再报错

情况2：

类似场景3的解决步骤

（1）startup mount

（2）查询redo情况

set lines 400 pages 9999

col MEMBER for a50

select v1.status, v1.group#, v1.bytes/1024/1024/1024,member,thread# ,sequence#, to_char(first_change#),to_char(NEXT_CHANGE#) from v$log v1, v$logfile v2 where v1.group# = v2.group# order by thread#, v1.group#, member ;

（3）recover database until cancel;

（4）alter database open RESETLOGS;

可能会报 ORA-01194: file 1 needs more recovery to be consistent错

（5）配置隐含参数推scn和跳过redo

alter system set event="21307096 trace name context forever, level 3" scope=spfile;

alter system set "_allow_resetlogs_corruption" = true scope=spfile;

（6）重启到mount

shutdown immediate

startup mount

（7）alter database open RESETLOGS;

此时open成功且alert日志没有报错

4、风险评估

情况1：

此种情况下，并不会造成数据丢失的风险

情况2：

可能有redo未落盘的情况，导致数据丢失

场景3：被删的redo组无冗余（CURRENT/ACTIVE的redo组）

1、构造故障场景

（1）查看当前redo配置

set lines 400 pages 9999

col MEMBER for a50

select v1.status, v1.group#, v1.bytes/1024/1024/1024,member,thread# ,sequence#, to_char(first_change#),to_char(NEXT_CHANGE#) from v$log v1, v$logfile v2 where v1.group# = v2.group# order by thread#, v1.group#, member ;

（2）将ACTIVE和CURRENT redo组对应的logfile删除

（3）多切几次归档，数据库会自动terminate

alter system switch logfile;

2、解决步骤

（1）将数据库起到mount，并查询redo组状态

startup mount

set lines 400 pages 9999

col MEMBER for a50

select v1.status, v1.group#, v1.bytes/1024/1024/1024,member,thread# ,sequence#, to_char(first_change#),to_char(NEXT_CHANGE#) from v$log v1, v$logfile v2 where v1.group# = v2.group# order by thread#, v1.group#, member ;

发现缺

（2）尝试clear CURRENT/ACTIVE的日志组

alter database clear unarchived logfile group 1;

alter database clear unarchived logfile group 2;

报错如下：

（3）recover数据库

recover database until cancel;

选择AUTO

（4）resetlogs启动数据库

alter database open resetlogs;

可能的报错

ORA-00600: internal error code, arguments: [kcbzib_kcrsds_1], [], [], [], [],[], [], [], [], [], [], []

--scn不一致，需要推进scn

ORA-01194: file 1 needs more recovery to be consistent

--scn不一致，需要推进scn

ORA-00600: internal error code, arguments: [4194], [7], [6], [], [], [], [], [], [], [], [], []

--undo回滚段与redo不一致，需要重建undo

（5）处理方法

（6）后续操作

drop tablespace UNDOTBS4 including contents and datafiles;

如果在drop过程中报如下错误：

ORA-01548: active rollback segment '_SYSSMU6_3592678216$' found, terminate dropping tablespace

查看当前异常的回滚段：

select segment_name, status, tablespace_name from dba_rollback_segs where status not in ('ONLINE', 'OFFLINE');

需要设置隐含参数，_offline_rollback_segments，强制offline异常的回滚段

create pfile='/oracle/pfile.ora' from spfile;

修改/oracle/pfile.ora，添加

*._offline_rollback_segments=(_SYSSMU6_3592678216$,_SYSSMU7_1736514206$)

startup pfile='/oracle/pfile.ora'

drop tablespace UNDOTBS4 including contents and datafiles;

（7）恢复原参数

shutdown immediate

startup

alter system reset event;

alter system reset "_allow_resetlogs_corruption";

将新建undo数据文件改成原来的大小（如果原来的undo表空间大，就要添加数据文件）

alter database datafile '/oracle/oradata/SH3/undotbs2.dbf' resize 30G;

shutdown immediate

startup

其他可能的情况：

情况1：

recover database until cancel时，报ORA-16433: The database or pluggable database must be opened in read/write mode错

需要重建控制文件

CREATE CONTROLFILE REUSE DATABASE "SH1" RESETLOGS NOARCHIVELOG

MAXLOGFILES 16

MAXLOGMEMBERS 3

MAXDATAFILES 8192

MAXINSTANCES 8

MAXLOGHISTORY 292

LOGFILE

GROUP 1 '/oracle/oradata/SH1/redo01.log' SIZE 1024M BLOCKSIZE 512,

GROUP 2 '/oracle/oradata/SH1/redo02.log' SIZE 1024M BLOCKSIZE 512,

GROUP 3 '/oracle/oradata/SH1/redo03.log' SIZE 1024M BLOCKSIZE 512

-- STANDBY LOGFILE

DATAFILE

'/oracle/oradata/SH1/system01.dbf',

'/oracle/oradata/SH1/sysaux01.dbf',

'/oracle/oradata/SH1/sysaux02.dbf',

'/oracle/oradata/SH1/sysaux03.dbf',

'/oracle/oradata/SH1/undotbs04.dbf',

'/oracle/oradata/SH1/users01.dbf',

'/oracle/oradata/SH1/datafile/o1_mf_ceshi_jrcs6jhz_.dbf',

'/oracle/oradata/SH1/datafile/o1_mf_idx_cc_jrctcw1o_.dbf',

'/oracle/oradata/SH1/datafile/o1_mf_sys_shar_jrcs3zdr_.dbf',

'/oracle/oradata/SH1/datafile/o1_mf_tab_cc_jrct5r0q_.dbf',

'/oracle/oradata/SH1/datafile/o2_mf_tab_cc_jrct5r0q_.dbf'

CHARACTER SET AL32UTF8

;

然后

recover database using backup controlfile until cancel;

CANCEL

alter database open resetlogs;

ALTER TABLESPACE TEMP ADD TEMPFILE '/oracle/oradata/SH1/temp01.dbf' REUSE;

ALTER TABLESPACE TEMP ADD TEMPFILE '/oracle/oradata/SH1/temp02.dbf' REUSE;

ALTER TABLESPACE TEMP ADD TEMPFILE '/oracle/oradata/SH1/temp03.dbf' REUSE;

情况2：

处理完成后有些索引块损坏

select object_name,owner,object_type from dba_objects where object_id=1139870;

将索引drop掉重建即可解决（rebuild online不要用，有时无效）

4、风险评估

此种情况会导致数据丢失或者可能坏块，生产环境最好恢复之后重建数据库