史上最全，呕心沥血总结oracle推进SCN方法（六）

作者介绍：老苏，10余年DBA工作运维经验，擅长Oracle、MySQL、PG数据库运维（如安装迁移，性能优化、故障应急处理等）
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前面介绍了4种推进SCN方法
（1）event 10015 来增加 scn 的值
（2）隐含参数_minimum_giga_scn 来增加 scn 的值
（3）gdb/dbx 来直接修改内存中的值
（4）使用oradebug poke 直接修改内存中的值
（5）通过修改控制文件来修改 scn 的值

现在来说一下oracle推进SCN方法6：通过修改数据文件头来修改 scn 的值

1、查看当前SCN

--最好将数据库启动到mount状态
SQL> startup mount;
ORACLE instance started.Total System Global Area 3691200512 bytes
Fixed Size		    2258680 bytes
Variable Size		  788531464 bytes
Database Buffers	 2885681152 bytes
Redo Buffers		   14729216 bytes
Database mounted.
SQL> select checkpoint_change# from v$database;CHECKPOINT_CHANGE#
------------------3433886
SQL> col name for a80
SQL> set linesize 400;
SQL> select file#,name from v$datafile;FILE# NAME
---------- --------------------------------------------------------------------------------1 /u01/oradata/dbbbed/system01.dbf2 /u01/oradata/dbbbed/sysaux01.dbf3 /u01/oradata/dbbbed/undotbs01.dbf4 /u01/oradata/dbbbed/users01.dbf5 /u01/oradata/dbbbed/tbst01.dbf6 /u01/oradata/dbbbed/szr01.dbf7 /u01/oradata/dbbbed/mssm01.dbf8 /u01/oradata/dbbbed/test0529.dbf8 rows selected.SQL> col name for a60;
set linesize 400;
select a.file#,a.name,(select checkpoint_change# from v$database) system_ckpt_scn,a.checkpoint_change# df_ckpt_scn,a.last_change# end_scn,b.checkpoint_change# start_scn,b.rSQL> SQL>   2    3    4    5    6    7  ecover,a.statusfrom v$datafile a, v$datafile_header bwhere a.file# = b.file#;  8    9   10  FILE# NAME 							SYSTEM_CKPT_SCN DF_CKPT_SCN    END_SCN	START_SCN REC STATUS
---------- ------------------------------------------------------------ --------------- ----------- ---------- ---------- --- -------1 /u01/oradata/dbbbed/system01.dbf					3433886     3433886    3433886	  3433886 NO  SYSTEM2 /u01/oradata/dbbbed/sysaux01.dbf					3433886     3433886    3433886	  3433886 NO  ONLINE3 /u01/oradata/dbbbed/undotbs01.dbf					3433886     3433886    3433886	  3433886 NO  ONLINE4 /u01/oradata/dbbbed/users01.dbf					3433886     3433886    3433886	  3433886 NO  ONLINE5 /u01/oradata/dbbbed/tbst01.dbf					3433886     3433886    3433886	  3433886 NO  ONLINE6 /u01/oradata/dbbbed/szr01.dbf					3433886     3433886    3433886	  3433886 NO  ONLINE7 /u01/oradata/dbbbed/mssm01.dbf					3433886     3433886    3433886	  3433886 NO  ONLINE8 /u01/oradata/dbbbed/test0529.dbf					3433886     3433886    3433886	  3433886 NO  ONLINE

2、bbed修改文件头SCN

–将数据文件加入bbed filelist,使用bbed进行编辑

$ cat filelist.txt 
1	/u01/oradata/dbbbed/system01.dbf	775946240
2	/u01/oradata/dbbbed/sysaux01.dbf	513802240
3	/u01/oradata/dbbbed/undotbs01.dbf	78643200
4	/u01/oradata/dbbbed/users01.dbf	5242880
5	/u01/oradata/dbbbed/tbst01.dbf	10485760
6	/u01/oradata/dbbbed/szr01.dbf	10485760
7      /u01/oradata/dbbbed/mssm01.dbf   10485760
8      /u01/oradata/dbbbed/test0529.dbf 5242880$ bbedBBED: Release 2.0.0.0.0 - Limited Production on Thu Jun 6 11:01:03 2024Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.************* !!! For Oracle Internal Use only !!! ***************BBED> infoFile#  Name                                                        Size(blks)-----  ----                                                        ----------1  /u01/oradata/dbbbed/system01.dbf                                 947202  /u01/oradata/dbbbed/sysaux01.dbf                                 627203  /u01/oradata/dbbbed/undotbs01.dbf                                 96004  /u01/oradata/dbbbed/users01.dbf                                    6405  /u01/oradata/dbbbed/tbst01.dbf                                    12806  /u01/oradata/dbbbed/szr01.dbf                                     12807  /u01/oradata/dbbbed/mssm01.dbf                                    12808  /u01/oradata/dbbbed/test0529.dbf                                   640

–将所有数据文件头的scn由3433886改成4433886

SQL> select to_char(3433886,'xxxxxxxxxxx'),to_char(4433886,'xxxxxxxxxxxx') from dual;TO_CHAR(3433 TO_CHAR(44338
------------ -------------34659e	    43a7de
BBED> set file 1 block 1FILE#          	1BLOCK#         	1
BBED> p kcvfhckp
struct kcvfhckp, 36 bytes                   @484     struct kcvcpscn, 8 bytes                 @484     ub4 kscnbas                           @484      0x0034659eub2 kscnwrp                           @488      0x0000ub4 kcvcptim                             @492      0x45cb01f0ub2 kcvcpthr                             @496      0x0001union u, 12 bytes                        @500     struct kcvcprba, 12 bytes             @500     ub4 kcrbaseq                       @500      0x00000007ub4 kcrbabno                       @504      0x00000223ub2 kcrbabof                       @508      0x0010
##注意上面的红色字体部分，我们需要将offset 484 这个地方的值改成0x0043a7deBBED> assign dba 1,1 kcvfh.kcvfhckp.kcvcpscn.kscnbas  = 0x0043a7de
或者直接用10进制的也行
BBED> assign dba 1,1 kcvfh.kcvfhckp.kcvcpscn.kscnbas  = 4433886
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
ub4 kscnbas                                 @484      0x0043a7deBBED> p kcvfhckp
struct kcvfhckp, 36 bytes                   @484     struct kcvcpscn, 8 bytes                 @484     ub4 kscnbas                           @484      0x0043a7de
继续修改其他的数据文件
assign dba 2,1 kcvfh.kcvfhckp.kcvcpscn.kscnbas  = 0x0043a7de
assign dba 3,1 kcvfh.kcvfhckp.kcvcpscn.kscnbas  = 0x0043a7de
assign dba 4,1 kcvfh.kcvfhckp.kcvcpscn.kscnbas  = 0x0043a7de
assign dba 5,1 kcvfh.kcvfhckp.kcvcpscn.kscnbas  = 0x0043a7de
assign dba 6,1 kcvfh.kcvfhckp.kcvcpscn.kscnbas  = 0x0043a7de
assign dba 7,1 kcvfh.kcvfhckp.kcvcpscn.kscnbas  = 0x0043a7de
assign dba 8,1 kcvfh.kcvfhckp.kcvcpscn.kscnbas  = 0x0043a7de

请添加图片描述
–保存修改

BBED> sum apply dba 1,1
Check value for File 1, Block 1:
current = 0x73a2, required = 0x73a2BBED> sum apply dba 2,1
Check value for File 2, Block 1:
current = 0x06ea, required = 0x06eaBBED> sum apply dba 3,1
Check value for File 3, Block 1:
current = 0x2aca, required = 0x2acaBBED> sum apply dba 4,1
Check value for File 4, Block 1:
current = 0x44a3, required = 0x44a3BBED> sum apply dba 5,1
Check value for File 5, Block 1:
current = 0x4dbe, required = 0x4dbeBBED> sum apply dba 6,1
Check value for File 6, Block 1:
current = 0x4c4b, required = 0x4c4bBBED> sum apply dba 7,1
Check value for File 7, Block 1:
current = 0x7012, required = 0x7012BBED> sum apply dba 8,1
Check value for File 8, Block 1:
current = 0xa710, required = 0xa710

3、查看修改后的SCN

--打开数据库
SQL> alter database open;Database altered.--查看数据文件头的scn
SQL> select checkpoint_change# from v$datafile_header;CHECKPOINT_CHANGE#
------------------443388744338874433887443388744338874433887443388744338878 rows selected.SQL> col name for a60;
set linesize 400;
select a.file#,a.name,(select checkpoint_change# from v$database) system_ckpt_scn,a.checkpoint_change# df_ckpt_scn,a.last_change# end_scn,b.checkpoint_change# start_scn,b.rSQL> SQL>   2    3    4    5    6    7  ecover,a.statusfrom v$datafile a, v$datafile_header bwhere a.file# = b.file#;  8    9   10  FILE# NAME 							SYSTEM_CKPT_SCN DF_CKPT_SCN    END_SCN	START_SCN REC STATUS
---------- ------------------------------------------------------------ --------------- ----------- ---------- ---------- --- -------1 /u01/oradata/dbbbed/system01.dbf					4433887     4433887		  4433887 NO  SYSTEM2 /u01/oradata/dbbbed/sysaux01.dbf					4433887     4433887		  4433887 NO  ONLINE3 /u01/oradata/dbbbed/undotbs01.dbf					4433887     4433887		  4433887 NO  ONLINE4 /u01/oradata/dbbbed/users01.dbf					4433887     4433887		  4433887 NO  ONLINE5 /u01/oradata/dbbbed/tbst01.dbf					4433887     4433887		  4433887 NO  ONLINE6 /u01/oradata/dbbbed/szr01.dbf					4433887     4433887		  4433887 NO  ONLINE7 /u01/oradata/dbbbed/mssm01.dbf					4433887     4433887		  4433887 NO  ONLINE8 /u01/oradata/dbbbed/test0529.dbf					4433887     4433887		  4433887 NO  ONLINE8 rows selected.--查看数据库的scn
SQL> select current_scn from v$database;CURRENT_SCN
-----------4434186

可以看到，SCN已修改，成功推进SCN。

链接：
史上最全，呕心沥血总结oracle推进SCN方法（一）
史上最全，呕心沥血总结oracle推进SCN方法（二）
史上最全，呕心沥血总结oracle推进SCN方法（三）
史上最全，呕心沥血总结oracle推进SCN方法（四）
史上最全，呕心沥血总结oracle推进SCN方法（五）

请添加图片描述