Github user nickwallen commented on the issue:
https://github.com/apache/metron/pull/740
> so, what happens if we modify a field via %define from a stellar shell
started with -z ?
If you loaded GLOBAL_CONFIG with -z, then `%define`'d the same value, that
value would get overridden in the current REPL session only. It does not
change anything in Zk. If you restarted your REPL, then the value would go
back to what is in Zk.---
