These views summarize file I/O, grouped by user and event type. By default, rows are sorted by user and descending total latency.
          The user_summary_by_file_io_type
          and
          x$user_summary_by_file_io_type
          views have these columns:
- user- The client user name. Rows for which the - USERcolumn in the underlying Performance Schema table is- NULLare assumed to be for background threads and are reported with a host name of- background.
- event_name- The file I/O event name. 
- total- The total number of occurrences of the file I/O event for the user. 
- latency- The total wait time of timed occurrences of the file I/O event for the user. 
- max_latency- The maximum single wait time of timed occurrences of the file I/O event for the user.