Project changes happen all the time in the business world. You must be able to adapt to the ever changing world and be able to do it on the fly. Planning details are not always set in stone. 

I haven’t really experienced a lot of design change when I was working in the industry, but I’ve come across a couple changes that are related to the SOPs. They were mostly to improve the SOP or make the process more efficient. These were considered as non-essential design change (NDC). I have not experienced any design change number (DCN) or engineering change order (ECO), but I am hoping to do so when I get back into the industry in the future to gain more experience. It was quite interesting to see how common ECOs are from the comments.