Agreements - Do you provide a Product Owner?
There are lots of stakeholders in a software project. Users, Marketing, Managers, they all have requirements for the new system but if the spec becomes a free-for-all, it is more likely the project will be steered off-course.
Select a "Product Owner" - who is the sole person able to make scope decisions and authorize work.
Remember it's all too tempting to allow the DBA to authorise work without seeking proper authority, so insist that your software consultants follow the standard on getting work approved through a Product Owner.