SET @start_global_value = @@global.XENGINE_COMPACTION_MODE;
SELECT @start_global_value;
@start_global_value
0
"Trying to set variable @@global.XENGINE_COMPACTION_MODE to 444. It should fail because it is readonly."
SET @@global.XENGINE_COMPACTION_MODE   = 444;
ERROR HY000: Variable 'xengine_compaction_mode' is a read only variable