Updating Sitecore can be a nightmare if you do not take the time to properly plan your update. First at all, you have to be sure about the current Sitecore version that you have and the version that you want to upgrade to. For this, just have to go to the Sitecore Login page and check the info in the right column.
Second, go to Sitecore’s SDN (Sitecore Developer Network) and navigate to the new version. For example, if you want to update from Sitecore.NET 6.5.0 (rev. 110602) to 7.0 rev.140408 (7.0 Service Pack-1), you’d follow this path: SDN à Products à Sitecore CMS à Sitecore 7 à CMS+DMS Downloads/Updates à 7.0 rev.140408 (7.0 Service Pack-1)
To upgrade from Sitecore 6.5 to Sitecore 7.0 you have to check the prerequisites:
Sitecore 7.0 requires at least Sitecore 6.6 rev. 120918, so you would have to execute the upgrade process twice (do the Sitecore 6.5 to Sitecore 6.6 upgrade first and then upgrade to Sitecore 7.0).
Lucene upgrade and related modules
Sitecore 6.5 uses Lucene.NET 184.108.40.206, but Sitecore 6.6 or greater uses a new version of Lucene, 2.9.4. This can cause many issues in the upgrade process because some modules use Lucene like Indexviewer or Weblog. In addition, there could be custom code that uses Lucene. To handle this, you’d have to uninstall these modules first (How to uninstall a Sitecore Package) and remove or comment all the code that refers to Lucene. Then run the update package. Then you would re-install the modules with the new versions available. If you don’t do this, the UpdateInstallationWizard will not let you update your Sitecore version (error shown below):
Upgrading your Sitecore version is a great way to ensure you can take advantage of Sitecore’s latest features as well as help keep your site secure; however, if you do not take the proper steps before your upgrade, you’ll end up wasting time and resources trying to update your site.
Upgrading from Sitecore 6.5 to 6.6 can raise some issues, more specifically, issues related to the Lucene search module. This module has changed much of its functionality between version 2.3.1 (Sitecore 6.5) and version 220.127.116.11 (Sitecore 6.6). Some of Sitecore’s other modules, like Indexviewer and Weblog, use Lucene as well, so you can run into issues with those modules during your update as well.
The Taxonomy module is an open module whose code can be found in Github. Because of this, you can download the code, change the references to the new Lucene version (18.104.22.168), and replace the .dll generated inside your site’s bin folder.
Even with this workaround, some people still have problems trying to make the update installation package work. This is because there is something else that is not included in the Sitecore update package. This is the new Sitecore.Client.dll. This file has a reference to Lucene’s old version and it has not been replaced in the upgrade process. You’ll need to download the Sitecore CMS+DMS code, go to the bin folder, and replace the Sitecore.Client.dll from 6.6 in your site. After you do this, you can finally move forward in the update process.
Upgrading Sitecore is not a complex process. However, some issues related to modules like Lucene can turn this into a nightmare. If you are planning to upgrade Sitecore 6.5 to Sitecore 6.6, please remember to uninstall all the modules and comment all of your code that has a reference to Lucene before running the upgrade process.