SET @start_global_value = @@global.XENGINE_COMPRESSION_OPTIONS;
SELECT @start_global_value;
@start_global_value
-14:1:0
"Trying to set variable @@global.XENGINE_COMPRESSION_OPTIONS to 444. It should fail because it is readonly."
SET @@global.XENGINE_COMPRESSION_OPTIONS   = 444;
ERROR HY000: Variable 'xengine_compression_options' is a read only variable