How to set TFS2008 Read Only after TFS2012 migration?

Dear all,

I must keep the old server TFS2008 read only after migration.

Also found few discussion online and possible solutions.

For eg: (Risk)

http://stackoverflow.com/questions/7208445/is-there-a-way-to-turn-a-tfs-instance-into-read-only-mode

For eg (Set source folder/file to lock)

http://msdn.microsoft.com/en-us/library/gg490760(v=vs.100).aspx

Do anybody have experience how to set TFS2008 read only after migration please?

After migration, all clients will point to new server tfs2012.

Other time may need to access back to old tfs2008 for references.

We have customized builds also.

Lee