sys Schema Views The  x$host_summary_by_file_io  view summarizes the same data but displays unformatted picosecond latencies: The view without the  x$  prefix is intended to provide output that is more user friendly and easier to read. The view with the  x$  prefix that displays the same values in raw form is intended more for use with other tools that perform their own processing on the data. Views without the  x$  prefix differ from the corresponding  x$  views in these ways: These views summarize statement activity, file I/O, and connections, grouped by host. The  host_summary  and  x$host_summary  views have these columns: The host from which the client connected. Rows for which the  HOST  column in the underlying Performance Schema table is  NULL  are assumed to be for background threads and are reported with a host name of  background . The total number of statements for the host. The total wait time of timed statements for the host. The average wait time per timed statement for the host. The total number of table scans for the host. • statements • statement_latency • statement_avg_latency • table_scans • host •Byte counts are formatted with size units using  format_bytes() . •Time values are formatted with temporal units using  format_time() . •SQL statements are truncated to a maximum display width using  format_statement() . •Path name are shortened using  format_path() . 28.4.3.1 The host_summary and x$host_summary Views mysql>  SELECT * FROM sys.host_summary_by_file_io; +------------+-------+------------+ | host | ios | io_latency | +------------+-------+------------+ | localhost | 67570 | 5.38 s | | background | 3468 | 4.18 s | +------------+-------+------------+ mysql>  SELECT * FROM sys.x$host_summary_by_file_io; +------------+-------+---------------+ | host | ios | io_latency | +------------+-------+---------------+ | localhost | 67574 | 5380678125144 | | background | 3474 | 4758696829416 | +------------+-------+---------------+ 5141