Oracle误删除了日志，我们公司的oracle数据库被人误删除了在线日志online redo

可以尝试使用PRM-DUL恢复无法打开的oracle数据库，也可以尝试如下手法来解决问题：

【Oracle数据恢复】Redo Log重做日志文件坏块Corruption的解决 ORA-16038 ORA-00354 ORA-00353 ORA-00367 ORA-01624

ORA-16038 log %s sequence# %s cannot be archived
ORA-354 corrupt redo log block header
ORA-353 log corruption near block change time
ORA-367 checksum error in log file header

[oracle@mlab2 ~]$ oerr ora 16038
16038, 00000, "log %s sequence# %s cannot be archived"
// *Cause: An attempt was made to archive the named file, but the
// file could not be archived. Examine the secondary error
// messages to determine the cause of the error.
// *Action: No action is required.

[oracle@mlab2 ~]$ oerr ora 354
00354, 00000, "corrupt redo log block header"
// *Cause: The block header on the redo block indicated by the accompanying
// error, is not reasonable.
// *Action: Do recovery with a good version of the log or do time based
// recovery up to the indicated time. If this happens when archiving,
// archiving of the problem log can be skipped by clearing the log
// with the UNARCHIVED option. This must be followed by a backup of
// every datafile to insure recoverability of the database.
[oracle@mlab2 ~]$ oerr ora 353
00353, 00000, "log corruption near block %s change %s time %s"
// *Cause: Some type of redo log corruption has been discovered. This error
// describes the location of the corruption. Accompanying errors
// describe the type of corruption.
// *Action: Do recovery with a good version of the log or do incomplete
// recovery up to the indicated change or time.
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[oracle@mlab2 ~]$ oerr ora 367
00367, 00000, "checksum error in log file header"
// *Cause: The file header for the redo log contains a checksum that does
// not match the value calculated from the file header as read from
// disk. This means the file header is corrupted
// *Action: Find the correct file and try again.

对于不同状态的在线日志文件online redo logfile 损坏/坏块，有不同的解决方案。
对于以下2种情况将不能drop online的redo logfile，他们是：
如果仅仅有2个redo logfile groups
损坏的redo logfile文件属于当前日志组 current logfile group; V$LOG.STATUS=CURRENT

解决方案大致如下：

可以通过clear 命令来清理有问题的日志文件，语法如下：
alter database clear logfile group ;
alter database clear logfile ‘';

例如：
alter database clear logfile group 1;
alter database clear unarchived logfile group 1;

对于status=current 或者 status=active的日志将无法被清理， 如果清理会报 ORA-01624:

SQL> alter database clear unarchived logfile group 5;
alter database clear unarchived logfile group 5
*
ERROR at line 1:
ORA-01624: log 5 needed for crash recovery of instance G10R25 (thread 1)
ORA-00312: online log 5 thread 1: '/s01/G10R25/onlinelog/o1_mf_5_954q1vdo_.log'
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[oracle@vrh8 ~]$ oerr ora 1624
01624, 00000, "log %s needed for crash recovery of instance %s (thread %s)"
// *Cause: A log cannot be dropped or cleared until the thread's checkpoint
// has advanced out of the log.
// *Action: If the database is not open, then open it. Crash recovery will
// advance the checkpoint. If the database is open force a global
// checkpoint. If the log is corrupted so that the database cannot
// be opened, it may be necessary to do incomplete recovery until
// cancel at this log.

对于status=active的日志较为简单，只要能顺利完成一个alter system checkpoint就可以将其状态改为INACTIVE之后再CLEAR。
对于status=current的online redo logfile则比较麻烦，一般需要动用隐藏参数”_ALLOW_RESETLOGS_CORRUPTION”

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这个问题不太严重，只要数据文件在，理论上，数据可以恢复，如果无法自行解决，可以联系：网页链接，每年处理过大量oracle各种恢复故障

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