Upgrading SharePoint Foundation
This section of the Microsoft SharePoint 2010 Software Development Kit (SDK) provides overview information for developers about upgrading Microsoft SharePoint Foundation. SharePoint Foundation provides two basic ways to upgrade a deployment, either through upgrading in-place from one version or build to the next, or through attaching a database to the current installation. For IT professional guidance about how to perform upgrade of a SharePoint deployment, see Upgrading to SharePoint Foundation 2010 on the Microsoft TechNet Web site.
There are various issues to consider when upgrading to the current version, depending on the kinds of customization that you made in the previous version. Visual Upgrade, which is a new feature in SharePoint Foundation 2010, allows you to perform an in-place upgrade gradually, so that you can verify step-by-step how well the customizations you made in the previous release work in the current release. For information about using the new visual upgrade feature, see Visual Upgrade.
SharePoint Foundation introduces Feature upgrade as the best method for upgrading Feature elements that you used in the previous version. For information about the new way to upgrade custom Features, see Upgrading Features.
The upgrade definition schema makes it possible to create upgrade definition files that map, or relate to, site definition files and resources that exist in the previous version to features in the new version. For information about using the upgrade definition schema, see Upgrade Definition Files.
For information about database attachment, see Perform a database attach upgrade to SharePoint Foundation 2010 on the Microsoft TechNet Web site.
SharePoint Foundation does not support extending database schemas, and its upgrade code assumes that databases have not been modified. Installations that violate this assumption may experience data loss when SharePoint Foundation upgrade code runs, and the upgrade may not succeed. Parties affected are responsible for reading in their unsupported data prior to the SharePoint upgrade code, and reinserting it after upgrade. Any schema changes that have been made must be removed from the database because SharePoint Foundation does not support upgrading a modified database.