SET @start_global_value = @@global.sync_relay_log; SELECT @start_global_value; @start_global_value 10000 select @@global.sync_relay_log; @@global.sync_relay_log 10000 select @@session.sync_relay_log; ERROR HY000: Variable 'sync_relay_log' is a GLOBAL variable show global variables like 'sync_relay_log'; Variable_name Value sync_relay_log 10000 show session variables like 'sync_relay_log'; Variable_name Value sync_relay_log 10000 select * from information_schema.global_variables where variable_name='sync_relay_log'; VARIABLE_NAME VARIABLE_VALUE SYNC_RELAY_LOG 10000 select * from information_schema.session_variables where variable_name='sync_relay_log'; VARIABLE_NAME VARIABLE_VALUE SYNC_RELAY_LOG 10000 set global sync_relay_log=1; select @@global.sync_relay_log; @@global.sync_relay_log 1 set session sync_relay_log=1; ERROR HY000: Variable 'sync_relay_log' is a GLOBAL variable and should be set with SET GLOBAL set global sync_relay_log=1.1; ERROR 42000: Incorrect argument type to variable 'sync_relay_log' set global sync_relay_log=1e1; ERROR 42000: Incorrect argument type to variable 'sync_relay_log' set global sync_relay_log="foo"; ERROR 42000: Incorrect argument type to variable 'sync_relay_log' set global sync_relay_log=0; select @@global.sync_relay_log; @@global.sync_relay_log 0 set global sync_relay_log=cast(-1 as unsigned int); Warnings: Warning 1292 Truncated incorrect sync_relay_log value: '18446744073709551615' select @@global.sync_relay_log; @@global.sync_relay_log 4294967295 SET @@global.sync_relay_log = @start_global_value; SELECT @@global.sync_relay_log; @@global.sync_relay_log 10000