What is Online Data? It's a bunch of files that usually updates every time NBA 2K12 release a new roster. Basically, your new roster will not function properly without the online data files.

How to Install Online Data:
1. Download the latest NBA 2K12 Online Data.
2. Extract / Unrar the file.
3. Open "Online Data" then open "downloads" folder.
4. Copy all the files inside "downloads" folder.
5. Start > Run > Type : %AppData% then press Enter
6. Open 2K Sports\NBA 2K12\Online Data\downloads
C:\Users\username\AppData\Roaming\2K Sports\NBA 2K12\Online Data\downloads
7. Paste the files in downloads folder (create one if you don't have 'downloads' folder)

Note: To make sure that NBA 2K12 will find the data files, You can also paste the files from the downloads folder to the game folder ("C:\Program Files\2K Sports\NBA 2K12")

Download Link: http://www.mediafire.com/?vgh2s36wesfxz74
This is the latest Online Data for NBA 2K12 PC version - June 28, 2012)