Hi MadiMo,
To be honest, I doubt you will find exact specifications and requirements on line. Even if you do, they are unlikely to be exactly what you are after. What exactly do you want them for? Bear in mind that no 2 database systems are alike, and using someone else's requirements to meet your own is a dangerous game.
If you want them because you are trying to build your own system for a project you are working on, you really will need to go and speak to your stakeholders.
If you don't know what to ask them, don't worry. That's why you talk to stakeholders for in the first place - to find out what is needed.
In general, you will need to find out:
a. Who uploads the data entries into the database?
b. What methods they use to update the entries?
c. Who owns the database, including who maintains it, looks after it, cleans it up etc. (Think of the database system as a small child!).
d. Who and what will interact with it (what other systems feed off of it, and how will they do that?
e. What reaction times are required?
f. Do you need to think about security for the database system? If so, what is required? Your Risk & Compliance team will have some input into that as well as the Head of IT Security.
g. How long are data entries kept, and what process is incorporated to delete redundant records?
h. Do the systems that feed off of the Database system have a priority and/or a expectation on how quick response times are?
I am sure there will be more questions, but they will be enough to give you an insight into how and what to look at to start off with. Who is responsible for actually building this system? Remember that you will need to touch base with them quite often to ensure that they have everything they need in order to build it.
If you really don't know who to ask (i.e you don't know how your stakeholders are/will be) start off with an obvious one first of all, and then ask them "Who else do you think I should be speaking to?"
Do you already have a similar system that you are replacing? If so, see if you can get hold of any documentation for it and use that as your 'As-Is" stance. However, owns that system will also be very useful to talk to them.