Indeed, DoD is our last line of defense…no, not the Department of Defense, I meant the Definition of Done!
in scrum, as we Sprint, we deliver a thing of value — an increment of the product that we are building — that is potentially releasable. 
Before it gets released, however, we have to check if it is really “Done” — it is prudent to check it against a standard that Scrum calls, the Definition of Done. If it is not “Done”, then it is not fit for release to production. In most cases, DoD is our last defense against a crappy code/feature/solution!
You can find DoD in various levels:
Team Level: Increment/Sprint. There is a Definition of Done for an Increment, or a Sprint. One example of a Definition of Done item is: “The story passed the acceptance criteria”… or “passed unit testing”…
Program Level: In SAFe, there has got to be a Definition of Done for a Program Increment (PI). One example of a Definition of Done item is: “Features passed their behavior / user acceptance tests”.
Large Solution Level (SAFe): for a Capability (Large Solution level that spans multiple PIs and Agile Release Trains (ARTs))… there has got to be a Definition of Done for this as well. One example of a Definition of Done item is: “The capability — features of which were delivered over several PIs — passed the behavior / user acceptance tests, end to end, across multiple ARTs”.
The worst nightmare of a product owner or a product manager or a business owner is when Agile teams that are part of a Solution (heaven forbid, Large Solution) claim that they are “Done”, yet the whole solution is failing… therefore cannot be released! Do you think that a “Definition of Done”. at the solution level. would have helped clarify — to all Agile teams involved in the solution — what a “Done” is?
Here is a good mantra for all: “We plan together, we commit together, we execute together, we deploy together, we release together… and we all know what the Definition of Done is!”
I leave you with a very good video… a very incisive explanation of the Definition of Done pattern: https://www.youtube.com/watch?v=NWXYIYONvkA
October 15, 2022: My new book, “SAFe Is Like …“, is now available on Amazon. 
You will get a FREE SIGNED COPY if/when you register, pay, and complete a class by the Lean Agile Guru.
