Bethune 2016-02-01
此告警信息是在11.之后出现,主要是防止Exadata 存储节点 I/O 读取数据达到 latency capping (延时上限)时会读取尝试读取其它镜像。是一个Exadata的自动调整策略,有效的提高的读取的数据的速度。 从错误信息来进程在读取asm 镜像块的时候发现比较慢从而去读取另外一个镜像块。建议检测cell节点是否有异常。 MOS 对此错误详细解释: This is a new feature now available in called 'Exadata I/O Latency Capping'. This feature helps eliminate any outliers due to slow reads and prevents read outliers that would otherwise have been visible to applications. It's possible that on rare occasion, disk drives or flash drives can display high latencies for a small duration while an internal recovery operation is running. With Exadata I/O Latency Capping enabled, the software automatically cancels the slow read and ASM will redirect the read to a mirror copy as long as it's not the very last copy. If no further I/O messages are reported in the RDBMS alert log, this means that I/O redirection was successful.