How to acces OS X server data from iOS

Can you be specific on what it is you're trying to do?

I'm guessing you don't actually mean 'all of the data' since that would include a lot of server-related stuff that isn't relevant to clients (e.g. components of the OS itself). iOS also doesn't have a 'traditional' file system, so mounting the file system to navigate hierarchies or copy files doesn't make a huge amount of sense, either - and most documents are only relevant with a corresponding application, which may or may not exist in iOS.

So what is your goal here? What are you trying to achieve?

You can setup a share on OS X Server 5 and check "iOS" under Access.

Next, on your iOS 9 device, go to Settings -> Mail, Contacts, Calendars and add an account. When prompted, select "Other" and then "Add OS X Server Account". After that, you can access your server like any other document provider on iOS.

Beware though that it tends to be flakey for time being.

Wikis connect to the wiki page, through browser. Calendar, add account under Settings/Mail,Calendars and contacts.