Steps such as immunizing ther database by multiplexing putting in different locations control files , using online redo logs and archiving redo logs are necessary to avoid a single point of failure 像通过多路复用（放在不同的位置）控制文件使数据库免疫、使用联机重做日志和归档重做日志这样的步骤，都是避免单点故障所必需的。
If you know that an archived redo log group has been damaged , immediately back up all datafiles so that you will have a whole database backup that does not require the damaged archived redo log 实际上，归档日志文件丢失并不可怕，只要及时发现，并且目前还没有文件损坏，还不需要进行完全恢复，则马上做一个全库备份，则丢失的归档日志文件不再需要。
Oracle online recovery depends a great deal on what is actually lost , for example , losing a group on online redo logs , losing a rollback segment data file , or corrumption of a data file for the system table space Oracle联机恢复很大程度上取决于实际丢失了什么，例如，在联机重做日志上丢失了一个组、丢失了回滚段数据文件或者system表空间的数据文件的损坏。
For a long running transaction when all logs are active , online redo logs will only be overwritten if either you manually archive the non - active online redo or that you have the arch process to do it for you 对于长期运行的事务，当所有日志都处于活动状态时，如果手动对非活动联机重做进行归档，或者让arch进程来为您完成这项工作，那么只需重写联机重做日志即可。
