“Seamless Updates”, first introduced in 2016 and installed on every Google Pixel phone, makes it possible to install firmware updates on a secondary partition while the phone remains in use. It eliminates downtime between firmware updates after a single reboot, after which the secondary partition becomes the most important and the update is already complete. It also serves as a failure if an update goes wrong – the system may revert to the previous partition.
Update notification on a Samsung Galaxy S21 Ultra
Google has backed down from this requirement, as it no longer appears in the Android CDD (Compatibility Definition Document). The CDD serves as a guideline for Android OEMs and provides a list of what Google needs from OEMs to make their devices compatible with the latest version of Android.
It is suspected that the requirement is supported by pressure from OEMs like Samsung, whose latest Galaxy S21 smartphones do not have the framework to support seamless updates. Android Police has confirmed that the new Samsung Galaxy S21 Ultra does not support this feature. While Google has previously planned to require the feature, the CDD states that OEMs ‘MUST’ support a / b system updates. The “a” and “b” refer to the same partitions that vary between firmware updates.
Without seamless updates, an Android device would have to spend a few minutes pausing on a bootloader without using any applications or making phone calls, not even emergencies. Samsung’s reasoning to delay such a feature is unknown.
Source • Via