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A small update is a product update that changes a few files or possibly adds some new content. A minor update is a product update that makes enough changes to warrant changing the product version for the product, whereas a major update is a product update with a large number of changes that warrants a change in the product code.
It‘s sometimes easier to think of a small update as a "hotfix" or Quick Fix Engineering (QFE) update, a minor update as a service pack, and a major update as a product upgrade.
Small and minor updates can be considered almost equal in that the only real difference is that a minor update has a change to the ProductVersion whereas a small update does not. The rules that they follow and application of the patch are the same. Application of small and minor update patches requires explicit reinstallations. Major updates are not subject to that limitation and a reinstallation is not required for patch application. Additionally small and minor update patches are limited in the changes that can be made to the feature-component structure for the package. Significant changes can be made to the feature-component structure in the scope of a major update.
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Major Upgrade vs. Minor Upgrade vs. Small Update