SET @start_global_value = @@global.gtid_purged;
SELECT @start_global_value;
@start_global_value

select @@global.gtid_purged;
@@global.gtid_purged

select @@session.gtid_purged;
ERROR HY000: Variable 'gtid_purged' is a GLOBAL variable
show global variables like 'gtid_purged';
Variable_name	Value
gtid_purged	
show session variables like 'gtid_purged';
Variable_name	Value
gtid_purged	
select * from information_schema.global_variables where variable_name='gtid_purged';
VARIABLE_NAME	VARIABLE_VALUE
GTID_PURGED	
select * from information_schema.session_variables where variable_name='gtid_purged';
VARIABLE_NAME	VARIABLE_VALUE
GTID_PURGED	
SET @@global.gtid_purged= '11111111-1111-1111-1111-111111111111:2';
ERROR HY000: @@GLOBAL.GTID_PURGED can only be set when @@GLOBAL.GTID_MODE = ON.
select @@global.gtid_purged;
@@global.gtid_purged

