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