27.12.8 Performance Schema Connection Tables 27.12.7.3 The events_transactions_history_long Table 27.12.7.2 The events_transactions_history Table Performance Schema Connection Tables 4988 The  events_transactions_history  table contains the  N  most recent transaction events that have ended per thread. Transaction events are not added to the table until they have ended. When the table contains the maximum number of rows for a given thread, the oldest thread row is discarded when a new row for that thread is added. When a thread ends, all its rows are discarded. The Performance Schema autosizes the value of  N  during server startup. To set the number of rows per thread explicitly, set the  performance_schema_events_transactions_history_size  system variable at server startup. The  events_transactions_history  table has the same columns and indexing as events_transactions_current . See Section 27.12.7.1, “The events_transactions_current Table” . TRUNCATE TABLE  is permitted for the  events_transactions_history  table. It removes the rows. For more information about the relationship between the three transaction event tables, see Section 27.9, “Performance Schema Tables for Current and Historical Events” . For information about configuring whether to collect transaction events, see Section 27.12.7, “Performance Schema Transaction Tables” . The  events_transactions_history_long  table contains the  N  most recent transaction events that have ended globally, across all threads. Transaction events are not added to the table until they have ended. When the table becomes full, the oldest row is discarded when a new row is added, regardless of which thread generated either row. The Performance Schema autosizes the value of  N  is autosized at server startup. To set the table size explicitly, set the  performance_schema_events_transactions_history_long_size  system variable at server startup. The  events_transactions_history_long  table has the same columns as events_transactions_current . See Section 27.12.7.1, “The events_transactions_current Table” . Unlike  events_transactions_current ,  events_transactions_history_long  has no indexing. TRUNCATE TABLE  is permitted for the  events_transactions_history_long  table. It removes the rows. For more information about the relationship between the three transaction event tables, see Section 27.9, “Performance Schema Tables for Current and Historical Events” . For information about configuring whether to collect transaction events, see Section 27.12.7, “Performance Schema Transaction Tables” . When a client connects to the MySQL server, it does so under a particular user name and from a particular host. The Performance Schema provides statistics about these connections, tracking them per account (user and host combination) as well as separately per user name and host name, using these tables: • accounts : Connection statistics per client account • hosts : Connection statistics per client host name • users : Connection statistics per client user name