sys Schema Progress Reporting The  sys  schema contains many views that summarize Performance Schema tables in various ways. Most of these views come in pairs, such that one member of the pair has the same name as the other member, plus a  x$  prefix. For example, the  host_summary_by_file_io  view summarizes file I/O grouped by host and displays latencies converted from picoseconds to more readable values (with units); +------------+-------+------------+ | host | ios | io_latency | +------------+-------+------------+ | localhost | 67570 | 5.38 s | | background | 3468 | 4.18 s | +------------+-------+------------+ mysql>  SELECT * FROM sys.host_summary_by_file_io; mysql>  SELECT * FROM sys.x$host_summary_by_file_io; +------------+-------+---------------+ | host | ios | io_latency | +------------+-------+---------------+ | localhost | 67574 | 5380678125144 | | background | 3474 | 4758696829416 | +------------+-------+---------------+ The  x$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 for humans 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. For additional information about the differences between non- x$  and  x$  views, see Section 28.4.3, “sys Schema Views” . To examine  sys  schema object definitions, use the appropriate  SHOW  statement or INFORMATION_SCHEMA  query. For example, to examine the definitions of the  session  view and format_bytes()  function, use these statements: However, those statements display the definitions in relatively unformatted form. To view object definitions with more readable formatting, access the individual  .sql  files found under the  scripts/sys_schema  in MySQL source distributions. Prior to MySQL 8.0.18, the sources are maintained in a separate distribution available from the  sys  schema development website at https://github.com/mysql/mysql-sys. Neither  mysqldump  nor  mysqlpump  dump the  sys  schema by default. To generate a dump file, name the sys  schema explicitly on the command line using either of these commands: To reinstall the schema from the dump file, use this command: The following  sys  schema views provide progress reporting for long-running transactions: Assuming that the required instruments and consumers are enabled, the  progress  column of these views shows the percentage of work completed for stages that support progress reporting. mysql>  SHOW CREATE VIEW sys.session; mysql>  SHOW CREATE FUNCTION sys.format_bytes; mysqldump --databases --routines sys > sys_dump.sql mysqlpump sys > sys_dump.sql mysql < sys_dump.sql processlist session x$processlist x$session 28.3 sys Schema Progress Reporting 5133