db file parallel read

等待事件 ：

db file parallel read

 

This happens during recovery.

发生在恢复过程中。

It can also happen during buffer prefetching, as an optimization (rather than performing multiple single-block reads).

也发生在buffer 预读取，作为多次单块读的优化方法。

Database blocks that need to be changed as part of recovery are read in parallel from the database.

在数据库恢复过程中需要改变的数据块以并行的方式读取

Wait Time: Wait until all of the I/Os are completed

 

This Wait Event is used when Oracle performs in parallel reads from multiple datafiles to non-contiguous buffers in memory (PGA or Buffer Cache).

当oracle从多个数据文件中读取到内存的buffer中去（PGA或buffer cache）。、

If this wait is an important component of Wait Time, follow the same guidelines as 'db file sequential read'.

如果此事件作为等待事件重要的组成部分，参考'db file sequential read'

 

Parameter

Description

files

This indicates the number of files to which the session is reading

blocks

This indicates the total number of blocks to be read

requests

This indicates the total number of I/O requests, which will be the same as blocks