推scn – Database SOS

前段时间开发了基于内存修改的patch scn小程序（修改oracle scn小工具(patch scn)），用来修改oracle数据库scn,实现快速调整oracle scn的功能（特别是在一些恢复的时候很有用）,最近对其功能进一步完善，扩展了通过修改oracle controlfile实现调整scn功能,简单测试如下
数据库当前scn情况

C:\Users\XFF>sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on 星期四 10月 6 21:50:32 2022

Copyright (c) 1982, 2013, Oracle.  All rights reserved.


连接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> set num 16
SQL> select checkpoint_change# from v$database;

CHECKPOINT_CHANGE#
------------------
      141743308712

SQL> shutdown immediate;
数据库已经关闭。
已经卸载数据库。
ORACLE 例程已经关闭。

通过工具一键修改oracle scn

启动库查看修改之后scn值

SQL> startup mount;
ORACLE 例程已经启动。

Total System Global Area 6413680640 bytes
Fixed Size                  2293216 bytes
Variable Size            1275068960 bytes
Database Buffers         5117050880 bytes
Redo Buffers               19267584 bytes
数据库装载完毕。
SQL> set num 16
SQL> select checkpoint_change# from v$database;

CHECKPOINT_CHANGE#
------------------
      141743339676

SQL> alter database open;

数据库已更改。

SQL> select checkpoint_change# from v$database;

CHECKPOINT_CHANGE#
------------------
      151743339602

数据库启动过程中scn会被改变，在mount的时候未发生改变
Patch_SCN下载:Patch_SCN下载
Patch_SCN使用说明:Patch_SCN使用说明
OraRecovery下载:OraRecovery下载
OraRecovery使用说明:OraRecovery使用说明

联系：手机/微信(+86 17813235971) QQ(107644445)

标题：ORA-01052: required destination LOG_ARCHIVE_DUPLEX_DEST is not specified 恢复思路

今天一网友找到我,说数据库恢复在推scn的过程中遇到了ORA-01052: required destination LOG_ARCHIVE_DUPLEX_DEST is not specified错误无法解决,让我给予支持.这不禁让我想起,现在由于数据库bug和dblink原因导致了很多数据库scn很大,距离天花板非常近,从而使得数据库恢复过程中无法直接简单的推scn,这里正好结合该例子,简单说明下ORA-01052故障的处理.类似文档以前也写过:ORA-01052发生原因的类似文章

由于坏块导致数据库进行实例恢复无法进行

Beginning crash recovery of 1 threads
Started redo scan
Completed redo scan
 read 1901 KB redo, 276 data blocks need recovery
Started redo application at
 Thread 1: logseq 1004, block 172771
Recovery of Online Redo Log: Thread 1 Group 2 Seq 1004 Reading mem 0
  Mem# 0: F:\APP\ADMINISTRATOR\ORADATA\XFF\REDO02.LOG
Fri May 29 10:59:56 2015
RECOVERY OF THREAD 1 STUCK AT BLOCK 439938 OF FILE 19
Fri May 29 11:00:00 2015
Exception [type: ACCESS_VIOLATION, UNABLE_TO_READ] [ADDR:0x2048] [PC:0x6215134, __intel_new_memcpy()+260]
Fri May 29 11:00:12 2015
Trace dumping is performing id=[cdmp_20150529110012]
Fri May 29 11:00:12 2015
Slave exiting with ORA-1172 exception
Errors in file f:\app\administrator\diag\rdbms\XFF\XFF\trace\XFF_p007_1612.trc:
ORA-01172: 线程 1 的恢复停止在块 439938 (在文件 19 中)
ORA-01151: 如果需要, 请使用介质恢复以恢复块和还原备份
Fri May 29 11:00:27 2015
ORA-01578: ORACLE 数据块损坏 (文件号 19, 块号 450245)
ORA-01110: 数据文件 19: 'F:\APP\ADMINISTRATOR\ORADATA\XFF\PSTORE_02.DBF'
ORA-10564: tablespace PSTORE
ORA-01110: 数据文件 19: 'F:\APP\ADMINISTRATOR\ORADATA\XFF\PSTORE_02.DBF'
ORA-10561: block type 'TRANSACTION MANAGED INDEX BLOCK', data object# 91642
ORA-00607: 当更改数据块时出现内部错误
ORA-00602: 内部编程异常错误
ORA-07445: 出现异常错误: 核心转储 [_intel_new_memcpy()+260] [ACCESS_VIOLATION] [ADDR:0x2048]
[PC:0x6215134] [UNABLE_TO_READ] []
Fri May 29 11:00:27 2015
Aborting crash recovery due to slave death, attempting serial crash recovery
RECOVERY OF THREAD 1 STUCK AT BLOCK 439938 OF FILE 19
Fri May 29 11:00:45 2015
Trace dumping is performing id=[cdmp_20150529110045]
Aborting crash recovery due to error 1172
ORA-1172 signalled during: alter database open...

设置_allow_resetlogs_corruption并resetlogs尝试打开数据库

Assigning activation ID 4272042346 (0xfea2316a)
Thread 1 opened at log sequence 1
  Current log# 1 seq# 1 mem# 0: F:\APP\ADMINISTRATOR\ORADATA\XFF\REDO01.LOG
Successful open of redo thread 1
MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set
Fri May 29 11:30:47 2015
SMON: enabling cache recovery
Fri May 29 11:30:47 2015
Errors in file f:\app\administrator\diag\rdbms\XFF\XFF\trace\XFF_ora_3004.trc  (incident=181236):
ORA-00600: ??????, ??: [2662], [3360], [2233437186], [3360], [2235447064], [4194545], [], [], [], [], [], []
Incident details in: f:\app\administrator\diag\rdbms\XFF\XFF\incident\incdir_181236\XFF_ora_3004_i181236.trc
Errors in file f:\app\administrator\diag\rdbms\XFF\XFF\trace\XFF_ora_3004.trc:
ORA-00704: ????????
ORA-00704: ????????
ORA-00600: ??????, ??: [2662], [3360], [2233437186], [3360], [2235447064], [4194545], [], [], [], [], [], []
Errors in file f:\app\administrator\diag\rdbms\XFF\XFF\trace\XFF_ora_3004.trc:
ORA-00704: ????????
ORA-00704: ????????
ORA-00600: ??????, ??: [2662], [3360], [2233437186], [3360], [2235447064], [4194545], [], [], [], [], [], []
Error 704 happened during db open, shutting down database
USER (ospid: 3004): terminating the instance due to error 704
Instance terminated by USER, pid = 3004
ORA-1092 signalled during: alter database open resetlogs...
opiodr aborting process unknown ospid (3004) as a result of ORA-1092

这里可以看到数据库通过设置_allow_resetlogs_corruption参数，进行不完全恢复,跳过数据库启动的实例恢复,然后强制拉库,然后遭遇大家熟悉的ORA-600[2662]错误,使得恢复失败,根据经验,通过推scn来绕过该错误

使用_minimum_giga_scn尝试推SCN

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
--------------------------------
*._minimum_giga_scn=13443
--------------------------------
SQL> startup pfile='/tmp/pfile'
ORACLE instance started.
Total System Global Area  236000356 bytes
Fixed Size                   451684 bytes
Variable Size             201326592 bytes
Database Buffers           33554432 bytes
Redo Buffers                 667648 bytes
Database mounted.
ORA-01052: required destination LOG_ARCHIVE_DUPLEX_DEST is not specified

通过运行Oracle Database Recovery Check检查发现数据库的scn已经非常大,距离天花板较近
_minimum_giga_scn
这里最大允许的推进的scn为13442.7,但是常规的最小的推scn的方法最小值为1024*1024*1024的倍数,因此这里遇到麻烦.
这里数据库遭遇了ORA-01052错误,导致推scn不成功,数据库无法正常启动.出现这类情况,由于scn可以增加的空间非常小,因此可以使用使用oradebug修改数据库scn或者直接修改控制文件scn的方式来精确控制推scn的值(可以实现任何值的scn增加,只要不超过天花板),也可以通过方法修改数据库scn距离天花板的距离,从而实现大幅度使用_minimum_giga_scn来推scn.另外还有一种解决方法:由于ORA-01052是由于scn过大导致(超过了数据库现在的天花板scn),因此出现了ORA-01052.所以另外一种变通的方法,就是通过调整数据库的天花板scn,从而使得_minimum_giga_scn可以继续推scn.在本次恢复中使用最为简单的增加天花板scn的方式来恢复(不过该方法恢复之后需要重建库,其实已经使用了隐含参数屏蔽redo恢复,本身就建议重建库保证数据字典一致性)

标签归档：推scn