ORA-00742: Log read detects lost write in thread number sequence number block number
Cause: Either a write issued by Oracle was lost by the underlying operating system or storage system or an Oracle internal error occurred.
Action: The trace file shows the lost write location. Dump the problematic log file to see whether it is a real lost write. Contact Oracle Support Services.
ORA-00742错误指的是Oracle中光标读取日志时发现账户中可能遗失了写入操作。
这个错误表示Oracle识别出来，在thread字符串、 sequence number字符串和 block number字符串的情况下可能遗失write操作。
1. 检查数据库告警日志，寻找对应I/O故障，确定是哪类故障导致ORA-00742出现；
2. 尝试解决I/O故障，并重启数据库；
3. 在数据库重启后，可以执行下面的SQL语句检查日志遗失情况：
SELECT thread#,sequence#,block#,bytes,members FROM v$log_history WHERE thread#=1 ORDER BY sequence#；
4. 如果检查发现遗失的Log，需要执行recovery进行数据库的恢复，请参考下面的文档：
http://www.oracle-base.com/articles/10g/transactions-loss-in-10g.php。