select @@global.performance_schema_events_waits_history_size;
@@global.performance_schema_events_waits_history_size
15
select @@session.performance_schema_events_waits_history_size;
ERROR HY000: Variable 'performance_schema_events_waits_history_size' is a GLOBAL variable
show global variables like 'performance_schema_events_waits_history_size';
Variable_name	Value
performance_schema_events_waits_history_size	15
show session variables like 'performance_schema_events_waits_history_size';
Variable_name	Value
performance_schema_events_waits_history_size	15
select * from information_schema.global_variables
where variable_name='performance_schema_events_waits_history_size';
VARIABLE_NAME	VARIABLE_VALUE
PERFORMANCE_SCHEMA_EVENTS_WAITS_HISTORY_SIZE	15
select * from information_schema.session_variables
where variable_name='performance_schema_events_waits_history_size';
VARIABLE_NAME	VARIABLE_VALUE
PERFORMANCE_SCHEMA_EVENTS_WAITS_HISTORY_SIZE	15
set global performance_schema_events_waits_history_size=1;
ERROR HY000: Variable 'performance_schema_events_waits_history_size' is a read only variable
set session performance_schema_events_waits_history_size=1;
ERROR HY000: Variable 'performance_schema_events_waits_history_size' is a read only variable
