Which two operations require undo data? (Choose two.) A) committing a transaction B) rolling back a transaction C) recovering from failed transactions D) recording a transaction to redo log files E) rolling forward during instance recovery
Answer: B,C 参照第一题解析,回退事务和恢复失败的事务时需要用到undo数据。A)提交事务的时候,Oracle 会把重做日志缓冲区刷新输出到磁盘。E)“前滚”的时候需要日志文件。
|