MySQL Cluster Configuration
If you want to change the configurations for MySQL Cluster, we recommend that you do it off peak. Even though it is generally safe to increase and decrease parameters, but decreasing a parameter such as DataMemory may have the effect that the memory will not be able to store all data.
See the official documentation provided by Oracle, https://docs.oracle.com/cd/E37745_01/html/E38170/toc.html for information about how to change the MySQL Cluster configurations.