1select @@global.performance_schema_max_statement_classes; 2@@global.performance_schema_max_statement_classes 3123 4select @@session.performance_schema_max_statement_classes; 5ERROR HY000: Variable 'performance_schema_max_statement_classes' is a GLOBAL variable 6show global variables like 'performance_schema_max_statement_classes'; 7Variable_name Value 8performance_schema_max_statement_classes 123 9show session variables like 'performance_schema_max_statement_classes'; 10Variable_name Value 11performance_schema_max_statement_classes 123 12select * from information_schema.global_variables 13where variable_name='performance_schema_max_statement_classes'; 14VARIABLE_NAME VARIABLE_VALUE 15PERFORMANCE_SCHEMA_MAX_STATEMENT_CLASSES 123 16select * from information_schema.session_variables 17where variable_name='performance_schema_max_statement_classes'; 18VARIABLE_NAME VARIABLE_VALUE 19PERFORMANCE_SCHEMA_MAX_STATEMENT_CLASSES 123 20set global performance_schema_max_statement_classes=1; 21ERROR HY000: Variable 'performance_schema_max_statement_classes' is a read only variable 22set session performance_schema_max_statement_classes=1; 23ERROR HY000: Variable 'performance_schema_max_statement_classes' is a read only variable 24