select @@global.host_cache_size;
@@global.host_cache_size
123
select @@session.host_cache_size;
ERROR HY000: Variable 'host_cache_size' is a GLOBAL variable
show global variables like 'host_cache_size';
Variable_name	Value
host_cache_size	123
show session variables like 'host_cache_size';
Variable_name	Value
host_cache_size	123
select * from information_schema.global_variables
where variable_name='host_cache_size';
VARIABLE_NAME	VARIABLE_VALUE
HOST_CACHE_SIZE	123
select * from information_schema.session_variables
where variable_name='host_cache_size';
VARIABLE_NAME	VARIABLE_VALUE
HOST_CACHE_SIZE	123
set global host_cache_size=1;
select @@global.host_cache_size;
@@global.host_cache_size
1
set global host_cache_size=12;
select @@global.host_cache_size;
@@global.host_cache_size
12
set global host_cache_size=0;
select @@global.host_cache_size;
@@global.host_cache_size
0
set session host_cache_size=1;
ERROR HY000: Variable 'host_cache_size' is a GLOBAL variable and should be set with SET GLOBAL
set global host_cache_size=123;
select @@global.host_cache_size;
@@global.host_cache_size
123