Hi. In previous jobs, i have used pt-online-schema-change quite a bit, normally testing the change the night before it went live. I have a very good understanding about how pt-online-schema-change works and i would like to understand the inner workings of alter_algorithm='NOCOPY'. If i can trust that as much as the percona script, i'm going to be happy happy person. Thanks. This is my reddit post. https://www.reddit.com/r/mariadb/comments/mx4e60/ptonlineschemachange_vs_alt... . I know we have a lot of great responders here, and if the answer comes here or on reddit, i will copy and paste for everyone's knowledge. Thanks all!