We have a few users that open Qlikview documents with open in server.
What we encounter is when they open a document the first time, it opens fast, but when they close the document and try to open it again Qlikview (few minutes after we closed it) is not responding and in most cases the document doesn't even open anymore.
NT Identity uses the Kerberos token that an AD domain controller creates when you first logon to a Windows domain. Sort of an actively selected Single Sign-On. Doesn't work if computer and server aren't both members of the same domain
Alternate Identity prepares a login url to autheticate to the QlikView Server using a typical login handshake. When a password is requested by the server, the client (QV Desktop) will present you with a password dialog and send whetever you enter in thatdialog to the server. This technique also works when the server is not a member of the AD domain, or when there isn't even a domain configured in your network.