never change a running system

Etymology
From the field of computing, likely from.

Proverb

 * 1) Do not change something while it is working (because there is a risk of breaking it).

Usage notes

 * This proverb is primarily used by non-native speakers of English.

Etymology
, possibly from the field of computing, although this origin is disputed.

Proverb

 * 1) if it ain't broke, don't fix it; leave well enough alone