how to modify scn with oradebug(windows)?
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一个朋友测试说windows 7 x64平台无法利用oradebug poke来推进scn。我这里简单测试了一下，是ok的。
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SQL> select * from v$version; BANNER ---------------------------------------------------------------- Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bi PL/SQL Release 10.2.0.4.0 - Production CORE 10.2.0.4.0 Production TNS for 64-bit Windows: Version 10.2.0.4.0 - Production NLSRTL Version 10.2.0.4.0 - Production |
上述信息是我的Oracle 版本，OS为win 7 x64. 下面是我的几个简单测试，供参考！请勿在生产环境测试！
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+++修改前8位，包含scn_base和scn_wrap SQL> startup mount ORACLE instance started. Total System Global Area 524288000 bytes Fixed Size 2067040 bytes Variable Size 310379936 bytes Database Buffers 205520896 bytes Redo Buffers 6320128 bytes Database mounted. SQL> oradebug setmypid Statement processed. SQL> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [0049C0950, 0049C0980) = 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 049C0630 0 0000000 SQL> select file#,checkpoint_change# from v$datafile; FILE# CHECKPOINT_CHANGE# ---------- ------------------ 1 1957838 2 1957838 3 1957838 4 1957838 5 1957838 6 1957838 6 rows selected. SQL> select to_char('1957888','xxxxxxxx') from dual; TO_CHAR(' --------- 1de000 SQL> oradebug poke 0x0049c0950 8 0x1de000 BEFORE: [0049C0950, 0049C0958) = 00000000 00000000 AFTER: [0049C0950, 0049C0958) = 001DE000 00000000 SQL> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [0049C0950, 0049C0980) = 001DE000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 049C0630 0 0000000 SQL> alter database open; Database altered. SQL> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [0049C0950, 0049C0980) = 001DE0BE 00000000 00000000 00000000 00000028 00000000 00000000 00000000 00000000 00000000 049C0630 0 0000000 SQL> select file#,checkpoint_change# from v$datafile; FILE# CHECKPOINT_CHANGE# ---------- ------------------ 1 1957889 2 1957889 3 1957889 4 1957889 5 1957889 6 1957889 6 rows selected. |
可以看到，成功利用oradebug poke推进了scn。 SCN值从之前的1957838 增加到1957889.
+++++修改scn_wrap来推进scn
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SQL> alter system switch logfile; System altered. SQL> select file#,checkpoint_change# from v$datafile; FILE# CHECKPOINT_CHANGE# ---------- ------------------ 1 1957889 2 1957889 3 1957889 4 1957889 5 1957889 6 1957889 6 rows selected. SQL> alter system checkpoint; System altered. SQL> select file#,checkpoint_change# from v$datafile; FILE# CHECKPOINT_CHANGE# ---------- ------------------ 1 1958109 2 1958109 3 1958109 4 1958109 5 1958109 6 1958109 6 rows selected. SQL> shutdown immediate Database closed. Database dismounted. ORACLE instance shut down. SQL> startup mount ORACLE instance started. Total System Global Area 524288000 bytes Fixed Size 2067040 bytes Variable Size 310379936 bytes Database Buffers 205520896 bytes Redo Buffers 6320128 bytes Database mounted. SQL> oradebug setmypid Statement processed. SQL> select file#,checkpoint_change# from v$datafile; FILE# CHECKPOINT_CHANGE# ---------- ------------------ 1 1958282 2 1958282 3 1958282 4 1958282 5 1958282 6 1958282 6 rows selected. SQL> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [0049C0950, 0049C0980) = 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 049C0630 0 0000000 SQL> oradebug poke 0x0049c0950 4 1 BEFORE: [0049C0950, 0049C0954) = 00000000 AFTER: [0049C0950, 0049C0954) = 00000001 SQL> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [0049C0950, 0049C0980) = 00000001 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 049C0630 0 0000000 SQL> alter database open; Database altered. SQL> select file#,checkpoint_change# from v$datafile; FILE# CHECKPOINT_CHANGE# ---------- ------------------ 1 1958283 2 1958283 3 1958283 4 1958283 5 1958283 6 1958283 6 rows selected. SQL> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [0049C0950, 0049C0980) = 001DE249 00000000 00000000 00000000 0000002A 00000000 00000000 00000000 00000000 00000000 049C0630 0 0000000 |
我们可以看到，虽然前面的scn_wrap修改成功了，但是其实scn 并没有推进成功。 看来windows 64位环境不能利用这种方式来推进SCN。
+++++能否使用32位平台的修改方法来直接修改scn_base呢 ？
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SQL> startup mount ORACLE instance started. Total System Global Area 524288000 bytes Fixed Size 2067040 bytes Variable Size 310379936 bytes Database Buffers 205520896 bytes Redo Buffers 6320128 bytes Database mounted. SQL> oradebug setmypid Statement processed. SQL> select file#,checkpoint_change# from v$datafile; FILE# CHECKPOINT_CHANGE# ---------- ------------------ 1 1959094 2 1959094 3 1959094 4 1959094 5 1959094 6 1959094 6 rows selected. SQL> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [0049C0950, 0049C0980) = 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 049C0630 0 0000000 SQL> oradebug poke 0x0049c0950 4 0x0001 BEFORE: [0049C0950, 0049C0954) = 00000000 AFTER: [0049C0950, 0049C0954) = 00000001 SQL> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [0049C0950, 0049C0980) = 00000001 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 049C0630 0 0000000 SQL> select to_char(checkpoint_change#,'XXXXXXXXXXXXXXXX') from v$database; TO_CHAR(CHECKPOIN ----------------- 1DE4B6 SQL> oradebug poke 0x0049c0954 4 0x001de4b9 BEFORE: [0049C0954, 0049C0958) = 00000000 AFTER: [0049C0954, 0049C0958) = 001DE4B9 SQL> oradebug DUMPvar SGA kcsgscn_ kcslf kcsgscn_ [0049C0950, 0049C0980) = 00000001 001DE4B9 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 049C0630 0 0000000 SQL> alter database open; alter database open * ERROR at line 1: ORA-03113: end-of-file on communication channel |
我们可以看到，利用修改32位平台的方式在这里是行不通的，报错了。我们来看下alert log的错误是什么？
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Tue Oct 14 15:46:29 2014 alter database open Tue Oct 14 15:46:30 2014 Repairing half complete open of thread 1 Tue Oct 14 15:46:30 2014 Errors in file g:\oracle_test\product\10.2.0\admin\roger\bdump\roger_lgwr_6176.trc: ORA-00600: ??????, ??: [2252], [58553], [1], [], [], [], [], [] Tue Oct 14 15:46:31 2014 Errors in file g:\oracle_test\product\10.2.0\admin\roger\bdump\roger_lgwr_6176.trc: ORA-00600: ??????, ??: [2252], [58553], [1], [], [], [], [], [] LGWR: terminating instance due to error 470 Tue Oct 14 15:46:31 2014 Errors in file g:\oracle_test\product\10.2.0\admin\roger\bdump\roger_dbw0_2540.trc: ORA-00470: LGWR ???????? |
大家非常熟悉的错误，这里不多说了。 测试而已，供参考，偶尔数据恢复时可以利用，请勿在生产环境随意测试！
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