[20171110]_allow_read_only_corruption参数.txt
--//昨天在修改查询隐含参数脚本时发现一个参数_allow_read_only_corruption,感觉应该可以在异常关闭的情况下以read only打开.
--//自己测试看看.
1.环境:
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
SYS@book> @ &r/hide _allow_read_only_corruption
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE
--------------------------- ------------------------------------------------ ------------- ------------- ------------
_allow_read_only_corruption allow read-only open even if database is corrupt TRUE FALSE FALSE
2.测试前准备:
SYS@book> create pfile='/tmp/init@.ora' from spfile ;
File created.
--//修改 /tmp/initbook.ora文件,加入如下内容:
*._allow_read_only_corruption=true
--//做一个异常关闭数据库.
SYS@book> shutdown abort ;
ORACLE instance shut down.
SYS@book> startup mount pfile='/tmp/init@.ora'
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
SYS@book> show parameter allow
NAME TYPE VALUE
--------------------------- ------- ------
_allow_read_only_corruption boolean TRUE
--//说明只要配置了参数在参数文件中,隐含参数实际上也可以使用show parameter.但是像前面带2个下划线参数,show parameter还是无
--//法查询.比如:
SYS@book> show parameter __java_pool_size
SYS@book> @ &r/hide __java_pool_size
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE
----------------- --------------------------------- ------------- ------------- ------------
__java_pool_size Actual size in bytes of java pool FALSE 4194304 4194304
SYS@book> alter database open read only;
alter database open read only
*
ERROR at line 1:
ORA-16005: database requires recovery
--//可以发现不行.也许需要_allow_resetlogs_corruption参数配合.
3.继续测试:
--//修改 /tmp/initbook.ora文件,加入如下内容:
*._allow_resetlogs_corruption=true
SYS@book> @ &r/logfile
GROUP# STATUS TYPE MEMBER IS_ GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
------ ---------- ---------- -------------------------------- --- ------ ------- --------- ----------- --------- ------- --- ---------- ------------- ------------------- ------------ -------------------
1 ONLINE /mnt/ramdisk/book/redo01.log NO 1 1 728 52428800 512 1 NO CURRENT 13277659048 2017-11-09 16:18:09 2.814750E+14
2 ONLINE /mnt/ramdisk/book/redo02.log NO 2 1 726 52428800 512 1 YES INACTIVE 13277630208 2017-11-09 09:54:47 13277632611 2017-11-09 10:18:14
3 ONLINE /mnt/ramdisk/book/redo03.log NO 3 1 727 52428800 512 1 YES INACTIVE 13277632611 2017-11-09 10:18:14 13277659048 2017-11-09 16:18:09
4 STANDBY /mnt/ramdisk/book/redostb01.log NO
5 STANDBY /mnt/ramdisk/book/redostb02.log NO
6 STANDBY /mnt/ramdisk/book/redostb03.log NO
7 STANDBY /mnt/ramdisk/book/redostb04.log NO
7 rows selected.
$ mv /mnt/ramdisk/book/redo01.log /mnt/ramdisk/book/redo01.log_xxx
--//这样避免找到redo文件.或者假象redo01.log文件损坏了.
SYS@book> shutdown abort ;
ORACLE instance shut down.
SYS@book> startup mount pfile='/tmp/init@.ora'
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
SYS@book> @ &r/hide allow_r%corrupt%
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE
--------------------------- ------------------------------------------------ ------------- ------------- ------------
_allow_read_only_corruption allow read-only open even if database is corrupt FALSE TRUE TRUE
_allow_resetlogs_corruption allow resetlogs even if it will cause corruption FALSE TRUE TRUE
SYS@book> alter database open read only;
alter database open read only
*
ERROR at line 1:
ORA-16005: database requires recovery
$ oerr ora 16005
16005, 00000, "database requires recovery"
// *Cause: The database requires recovery, and therefore cannot be opened for
// read-only access by this instance.
// *Action: Perform the necessary recovery and reopen for read-only access.
//
--//视乎与_allow_resetlogs_corruption无关,取消*._allow_resetlogs_corruption=true设置,重来..
SYS@book> shutdown abort ;
ORACLE instance shut down.
SYS@book> startup mount pfile='/tmp/init@.ora'
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
SYS@book> @ &r/hide allow_r%corrupt%
old 10: and lower(a.ksppinm) like lower('%&1%')
new 10: and lower(a.ksppinm) like lower('%allow_r%corrupt%%')
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE
--------------------------- ------------------------------------------------ ------------- ------------- -------------
_allow_read_only_corruption allow read-only open even if database is corrupt FALSE TRUE TRUE
_allow_resetlogs_corruption allow resetlogs even if it will cause corruption TRUE FALSE FALSE
SYS@book> recover database until cancel;
ORA-00279: change 13277663682 generated at 11/10/2017 09:14:12 needed for thread 1
ORA-00289: suggestion : /u01/app/oracle/archivelog/book/1_728_896605872.dbf
ORA-00280: change 13277663682 for thread 1 is in sequence #728
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
auto
ORA-00308: cannot open archived log '/u01/app/oracle/archivelog/book/1_728_896605872.dbf'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
ORA-00308: cannot open archived log '/u01/app/oracle/archivelog/book/1_728_896605872.dbf'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
ORA-01547: warning: RECOVER succeeded but OPEN RESETLOGS would get error below
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: '/mnt/ramdisk/book/system01.dbf'
SYS@book> alter database open read only;
alter database open read only
*
ERROR at line 1:
ORA-16005: database requires recovery
--//依旧不行.失望!!
4.看看正常关闭数据库丢失某个redo的情况呢?
$ mv /mnt/ramdisk/book/redo01.log_xxx /mnt/ramdisk/book/redo01.log
--//先恢复到正常状态.
SYS@book> shutdown abort ;
ORACLE instance shut down.
SYS@book> startup mount
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
SYS@book> @ &r/hide allow_r%corrupt%
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE
--------------------------- ------------------------------------------------ ------------- ------------- ------------
_allow_read_only_corruption allow read-only open even if database is corrupt FALSE TRUE TRUE
_allow_resetlogs_corruption allow resetlogs even if it will cause corruption TRUE FALSE FALSE
SYS@book> recover database until cancel;
ORA-00279: change 13277663682 generated at 11/10/2017 09:14:12 needed for thread 1
ORA-00289: suggestion : /u01/app/oracle/archivelog/book/1_728_896605872.dbf
ORA-00280: change 13277663682 for thread 1 is in sequence #728
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
/mnt/ramdisk/book/redo01.log
Log applied.
Media recovery complete.
SYS@book> alter database open ;
alter database open
*
ERROR at line 1:
ORA-01589: must use RESETLOGS or NORESETLOGS option for database open
SYS@book> alter database open NORESETLOGS;
Database altered.
--//这种情况下是可以NORESETLOGS打开的,因为redo文件设置回来了.
SYS@book> select open_mode from v$database ;
OPEN_MODE
-----------
READ WRITE
SYS@book> shutdown immediate ;
Database closed.
Database dismounted.
ORACLE instance shut down.
SYS@book> startup mount pfile='/tmp/init@.ora'
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
SYS@book> @ &r/logfile
GROUP# STATUS TYPE MEMBER IS_ GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
------ ------ ---------- -------------------------------- --- ------ ------- --------- ----------- --------- ------- --- ---------- ------------- ------------------- ------------ -------------------
1 ONLINE /mnt/ramdisk/book/redo01.log NO 1 1 728 52428800 512 1 YES INACTIVE 13277659048 2017-11-09 16:18:09 13277684336 2017-11-10 09:54:02
2 ONLINE /mnt/ramdisk/book/redo02.log NO 2 1 729 52428800 512 1 NO CURRENT 13277684336 2017-11-10 09:54:02 2.814750E+14
3 ONLINE /mnt/ramdisk/book/redo03.log NO 3 1 727 52428800 512 1 YES INACTIVE 13277632611 2017-11-09 10:18:14 13277659048 2017-11-09 16:18:09
4 STANDBY /mnt/ramdisk/book/redostb01.log NO
5 STANDBY /mnt/ramdisk/book/redostb02.log NO
6 STANDBY /mnt/ramdisk/book/redostb03.log NO
7 STANDBY /mnt/ramdisk/book/redostb04.log NO
7 rows selected.
--//当前是/mnt/ramdisk/book/redo02.log.
$ mv /mnt/ramdisk/book/redo02.log /mnt/ramdisk/book/redo02.log_xxx
SYS@book> alter database open read only ;
Database altered.
SYS@book> @ &r/hide allow_r%corrupt%
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE
--------------------------- ------------------------------------------------ ------------- ------------- ------------
_allow_read_only_corruption allow read-only open even if database is corrupt FALSE TRUE TRUE
_allow_resetlogs_corruption allow resetlogs even if it will cause corruption TRUE FALSE FALSE
--//^_^,这个参数意义不大,要在正常关闭的情况下,redo文件损坏的情况下,可以使用它打开数据库.
5.看看使用正常参数启动情况如何?
SYS@book> shutdown immediate ;
Database closed.
Database dismounted.
ORACLE instance shut down.
SYS@book> startup
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
ORA-03113: end-of-file on communication channel
Process ID: 18301
Session ID: 274 Serial number: 3
--//因为/mnt/ramdisk/book/redo02.log文件无法找到,启动失败.修改回来:
$ mv /mnt/ramdisk/book/redo02.log_xxx /mnt/ramdisk/book/redo02.log
SYS@book> startup
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
Database opened.
SYS@book> @ &r/hide allow_r%corrupt%
old 10: and lower(a.ksppinm) like lower('%&1%')
new 10: and lower(a.ksppinm) like lower('%allow_r%corrupt%%')
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE
--------------------------- ------------------------------------------------ ------------- ------------- ------------
_allow_read_only_corruption allow read-only open even if database is corrupt TRUE FALSE FALSE
_allow_resetlogs_corruption allow resetlogs even if it will cause corruption TRUE FALSE FALSE
总结:
1._allow_read_only_corruption参数意义不大,要在正常关闭的情况下,某个redo文件不存在或者损坏的情况下临时open read only打开.
2.一旦数据库文件头与控制文件当前scn不一致,需要恢复是无法使用它,read only打开的,怪不得很少见人提到这个参数.
--//补充测试redo损坏不是current的情况.
SYS@book> shutdown immediate ;
Database closed.
Database dismounted.
ORACLE instance shut down.
SYS@book> startup mount pfile='/tmp/init@.ora'
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
SYS@book> @ &r/logfile
GROUP# STATUS TYPE MEMBER IS_ GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
------ ---------- ---------- ------------------------------- --- ------ ------- --------- ----------- --------- ------- --- ---------- ------------- ------------------- ------------ -------------------
1 ONLINE /mnt/ramdisk/book/redo01.log NO 1 1 728 52428800 512 1 YES INACTIVE 13277659048 2017-11-09 16:18:09 13277684336 2017-11-10 09:54:02
2 ONLINE /mnt/ramdisk/book/redo02.log NO 2 1 729 52428800 512 1 NO CURRENT 13277684336 2017-11-10 09:54:02 2.814750E+14
3 ONLINE /mnt/ramdisk/book/redo03.log NO 3 1 727 52428800 512 1 YES INACTIVE 13277632611 2017-11-09 10:18:14 13277659048 2017-11-09 16:18:09
4 STANDBY /mnt/ramdisk/book/redostb01.log NO
5 STANDBY /mnt/ramdisk/book/redostb02.log NO
6 STANDBY /mnt/ramdisk/book/redostb03.log NO
7 STANDBY /mnt/ramdisk/book/redostb04.log NO
7 rows selected.
$ mv /mnt/ramdisk/book/redo03.log /mnt/ramdisk/book/redo03.log_xxx
SYS@book> alter database open ;
alter database open
*
ERROR at line 1:
ORA-03113: end-of-file on communication channel
Process ID: 18497
Session ID: 274 Serial number: 3
--//无法打开数据库.
SYS@book> startup mount pfile='/tmp/init@.ora'
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
SYS@book> alter database open read only ;
Database altered.
--//还原现场:
SYS@book> shutdown immediate ;
Database closed.
Database dismounted.
ORACLE instance shut down.
$ mv /mnt/ramdisk/book/redo03.log_xxx /mnt/ramdisk/book/redo03.log
SYS@book> startup
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
Database opened.