(Only applicable for previous version of QlikView such as 12.30 and earlier) Rename the .ini file (that is, change qvpr_<OldMachineName>.ini to qvpr_<NewMachineName>.ini).
Change all references to<OldMachineName> to <NewMachineName> in the QVPR .xml files.
Start the QlikView services on the new machine.
Do NOT use the QMC to change the Distribution Service Source Document paths, as doing so will potentially break the task links. If you need to change paths, go directly to the SourceFolderDocumentResource.xml in the QVPR and make the changes directly there to point to the new paths, do not change anything but the path information, as the GUID links must stay the same in order to keep the tasks aligned. An alternative to editing the XML file directly is to use the XML DB Viewer power tool which allows you to search as well as find/replace.
Shut down the old machine.
NOTE: If there have been any changes made to the QMS exe.config file, be certain those changes are documented somewhere, as they will need to be re-applied to the new QMS exe.config file post-upgrade. The upgrade uninstalls the 11.20 files and installs new 12.xx files, which means the exe.config will be removed and recreated without customizations. The QMS is unique in that it does not write changes to the programdata path like the other services, so be certain the customizations are documented and reapplied post-upgrade prior to bringing the services back online again.