Can you point me to a detailed Google document on how to migrate a large say 5M ...

blauwbilgorgel · on March 11, 2013

While 5 million pages is a very big number (that probably requires a lot more planning) this might be the Google document you are looking for:

http://support.google.com/webmasters/bin/answer.py?hl=en&...

  Moving your site
  If you're planning on moving your site to a new domain, 
  here are some tips that will help you retain your site's
  ranking in Google's search results.

Edit: http://www.mattcutts.com/blog/moving-to-a-new-web-host/ (2005)

http://googlewebmastercentral.blogspot.nl/2008/04/best-pract... (2008)

walshemj · on March 11, 2013

oh a single page how generous of them :-0

Matt_Cutts · on March 11, 2013

Also make sure you check out these videos:

http://www.youtube.com/watch?v=wATxftE8ooE

http://www.youtube.com/watch?v=r1lVPrYoBkA

and maybe http://www.youtube.com/watch?v=l7M22teF3Ho depending on your circumstances.