Performance Schema Table Descriptions 27.12.1 Performance Schema Table Reference 27.12 Performance Schema Table Descriptions 4939 •Miscellaneous tables. These do not fall into any of the other table groups. •Instance tables. These tables document what types of objects are instrumented. An instrumented object, when used by the server, produces an event. These tables provide event names and explanatory notes or status information. •Summary tables. These tables contain information aggregated over groups of events, including those that have been discarded from the history tables. •History tables. These tables have the same structure as the current events tables, but contain more rows. For example, for wait events,  events_waits_history  table contains the most recent 10 events per thread.  events_waits_history_long  contains the most recent 10,000 events. Other similar tables exist for stage, statement, and transaction histories. •Current events tables. The  events_waits_current  table contains the most recent event for each thread. Other similar tables contain current events at different levels of the event hierarchy: events_stages_current  for stage events,  events_statements_current  for statement events, and  events_transactions_current  for transaction events. •Setup tables. These tables are used to configure and display monitoring characteristics. •To retrieve from  performance_schema  tables, you must have the  SELECT  privilege. •To change those columns that can be modified, you must have the  UPDATE  privilege. •To truncate tables that can be truncated, you must have the  DROP  privilege. Because only a limited set of privileges apply to Performance Schema tables, attempts to use  GRANT ALL as shorthand for granting privileges at the database or table leval fail with an error: Instead, grant exactly the desired privileges: Tables in the  performance_schema  database can be grouped as follows: To change the sizes of the history tables, set the appropriate system variables at server startup. For example, to set the sizes of the wait event history tables, set  performance_schema_events_waits_history_size  and performance_schema_events_waits_history_long_size . mysql>  GRANT SELECT ON performance_schema.* TO ’u1’@’localhost’; Query OK, 0 rows affected (0.03 sec) mysql>  GRANT SELECT, UPDATE ON performance_schema.setup_instruments TO ’u2’@’localhost’; Query OK, 0 rows affected (0.02 sec) mysql>  GRANT ALL ON performance_schema.* TO ’u1’@’localhost’; ERROR 1044 (42000): Access denied for user ’root’@’localhost’ to database ’performance_schema’ mysql>  GRANT ALL ON performance_schema.setup_instruments TO ’u2’@’localhost’; ERROR 1044 (42000): Access denied for user ’root’@’localhost’ to database ’performance_schema’