AWR看直接路径都注意关注 SQL ordered by Physical Reads、Segments by Direct Physical Reads

direct path read不一定就是全部扫描的，参考MOS文档：

Direct path reads are generally used by Oracle when reading directly into PGA memory (as opposed to into the buffer cache). If asynchronous IO is supported (and in use) then Oracle can submit IO requests and continue processing. It can then pick up the results of the IO request later and will wait on "direct path read" until the required IO completes.

If asynchronous IO is not being used then the IO requests block until completed but these do not show as waits at the time the IO is issued. The session returns later to pick up the completed IO data but can then show a wait on "direct path read" even though this wait will return immediately.

Hence this wait event is very misleading as:

The total number of waits does not reflect the number of IO requests

The total time spent in "direct path read" does not always reflect the true wait time.

This style of read request is typically used for:

Sort IO (when a sort does not fit in memory)

Parallel Query slaves

Readahead (where a process may issue an IO request for a block it expects to need in the near future)

明白了，谢谢回复，手机编辑的还有一部分信息没有发出来。