Jonathan gives a pretty good description of how the packages fit together.
He left one out, however, which I'll mention.
https://docs.pylonsproject.org/projects/pyramid-retry/en/latest/
pyramid_retry wraps pyramid_tm and looks for failed transactions that
failed due to some
The sqlalchemy cookie cutter uses pyramid_tm to handle the transaction.
The docs on that package should answer all your questions:
https://docs.pylonsproject.org/projects/pyramid_tm/en/latest/
Basically what happens is this:
* the actual transaction management is provided by zope's
