[20181123]快速提升scn注意.txt

[20181123]快速提升scn注意.txt --//有时候修复oracle数据库,需要提升scn号,现在许多方法不能再用,最快的方式适用oradebug修改kcsgscn_地址内容. --//今天做这方面测试遇到一些问题,应该引起注意,特别scn_wrap>0的情况下.做一个记录. 1.环境: SYS@book> @ 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> set numw 12 SYS@book> select current_scn from v$database ;  CURRENT_SCN ------------  13813808388 SYS@book> @ tx 13813808388 32 select 13813808388,trunc(13813808388/power(2,32)) scn_wrap,mod(13813808388,power(2,32))  scn_base from dual  13813808388     SCN_WRAP     SCN_BASE SCN_WRAP16 SCN_BASE16 ------------ ------------ ------------ ---------- ----------  13813808388            3    928906500          3   375dfd04 SYS@book> oradebug setmypid Statement processed. SYS@book> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [06001AE70, 06001AEA0) = 375DFD2F 00000003 00000000 00000000 00000063 00000000 00000000 00000000 00000000 00000000 6001AB50 00000000 --//scn_wrap=3 2.千万不要一次修改完成. --//实际上scn占48位. SYS@book> shutdown immediate ; Database closed. Database dismounted. ORACLE instance shut down. SYS@book> startup mount ORACLE instance started. Total System Global Area    643084288 bytes Fixed Size                    2255872 bytes Variable Size               205521920 bytes Database Buffers            427819008 bytes Redo Buffers                  7487488 bytes Database mounted. SYS@book> oradebug setmypid Statement processed. SYS@book> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [06001AE70, 06001AEA0) = 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6001AB50 00000000 --//在mount状态看到是0.如果这样修改: SYS@book> oradebug poke 0x06001AE70 8 0x375DFD2F00000003 BEFORE: [06001AE70, 06001AE78) = 00000000 00000000 AFTER:  [06001AE70, 06001AE78) = 00000003 375DFD2F SYS@book> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [06001AE70, 06001AEA0) = 00000003 375DFD2F 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6001AB50 00000000 --//对比前面,可以发现实际上scn_wrap=0xFD2F,scn_base=0x00000003.这样scn提升太快了. SYS@book> alter database open ; alter database open * ERROR at line 1: ORA-03113: end-of-file on communication channel Process ID: 54638 Session ID: 274 Serial number: 3 --//数据库根本无法打开.alert.log报如下错误: Completed: ALTER DATABASE   MOUNT Fri Nov 23 10:41:19 2018 alter database open Fri Nov 23 10:41:19 2018 LGWR: STARTING ARCH PROCESSES Fri Nov 23 10:41:19 2018 ARC0 started with pid=22, OS id=54655 ARC0: Archival started LGWR: STARTING ARCH PROCESSES COMPLETE ARC0: STARTING ARCH PROCESSES Fri Nov 23 10:41:20 2018 ARC1 started with pid=23, OS id=54657 Errors in file /u01/app/oracle/diag/rdbms/book/book/trace/book_lgwr_54618.trc  (incident=2281965): ORA-00600: internal error code, arguments: [2252], [64815], [4], [3787], [3407085568], [], [], [], [], [], [], [] Incident details in: /u01/app/oracle/diag/rdbms/book/book/incident/incdir_2281965/book_lgwr_54618_i2281965.trc Use ADRCI or Support Workbench to package the incident. See Note 411.1 at My Oracle Support for error and packaging details. Errors in file /u01/app/oracle/diag/rdbms/book/book/trace/book_lgwr_54618.trc: ORA-00600: internal error code, arguments: [2252], [64815], [4], [3787], [3407085568], [], [], [], [], [], [], [] LGWR (ospid: 54618): terminating the instance due to error 470 Fri Nov 23 10:41:20 2018 System state dump requested by (instance=1, osid=54618 (LGWR)), summary=[abnormal instance termination]. System State dumped to trace file /u01/app/oracle/diag/rdbms/book/book/trace/book_diag_54604_20181123104120.trc Dumping diagnostic data in directory=[cdmp_20181123104120], requested by (instance=1, osid=54618 (LGWR)), summary=[abnormal instance termination]. Instance terminated by LGWR, pid = 54618 3.必须分2次完成修改: SYS@book> startup mount ORACLE instance started. Total System Global Area  643084288 bytes Fixed Size                  2255872 bytes Variable Size             205521920 bytes Database Buffers          427819008 bytes Redo Buffers                7487488 bytes Database mounted. SYS@book> oradebug setmypid Statement processed. SYS@book> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [06001AE70, 06001AEA0) = 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6001AB50 00000000 SYS@book> oradebug poke 0x06001AE70 4 0x376DFD2F BEFORE: [06001AE70, 06001AE74) = 00000000 AFTER:  [06001AE70, 06001AE74) = 376DFD2F SYS@book> oradebug poke 0x06001AE74 2 0x0003 BEFORE: [06001AE74, 06001AE78) = 00000000 AFTER:  [06001AE74, 06001AE78) = 00000003 SYS@book> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [06001AE70, 06001AEA0) = 376DFD2F 00000003 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6001AB50 00000000 --//如下修改1个字节也可以. SYS@book> oradebug poke 0x06001AE74 1 0x03 BEFORE: [06001AE74, 06001AE78) = 00000003 AFTER:  [06001AE74, 06001AE78) = 00000003 SYS@book> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [06001AE70, 06001AEA0) = 376DFD2F 00000003 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6001AB50 00000000 --//你可以发现等号后面实际上反过来排列,估计与intel endian有关. --//补充一些测试: SYS@book> oradebug poke 0x06001AE77 1 0x03 BEFORE: [06001AE74, 06001AE78) = 00000003 AFTER:  [06001AE74, 06001AE78) = 03000003 SYS@book> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [06001AE70, 06001AEA0) = 376DFD2F 03000003 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6001AB50 00000000 --//你可以发现0x06001AE77地址的内容,显示实际上开头. SYS@book> oradebug poke 0x06001AE77 1 0x00 BEFORE: [06001AE74, 06001AE78) = 03000003 AFTER:  [06001AE74, 06001AE78) = 00000003 SYS@book> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [06001AE70, 06001AEA0) = 376DFD2F 00000003 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6001AB50 00000000 SYS@book> alter database open ; Database altered. SYS@book> set numw 12 SYS@book> select current_scn from v$database ;  CURRENT_SCN ------------  13814857318 --//实际上修改后仔细再看看,这些细节错误都很容易避免.