Android 6.0 Marshmallow is beginning to make its way towards Sony's smartphone lineup. Initially, beta versions of the update have been released on a handful of smartphones including the Sony Xperia Z2, Z3, and Xperia Z3 Compact, but more recently the Android 6.0 update has left Sony's beta stages and publicly landed on the aforementioned handsets. Many improvements have been introduced by Marshmallow, but much to the surprise of numerous Sony enthusiasts, Sony's STAMINA battery mode has been removed in Android 6.0 and replaced by Google's Doze battery management system. Fortunately for Sony smartphone owners, the Japanese company has just confirmed that STAMINA mode will make its way back to Android 6.0 Marshmallow in one of the upcoming releases in Xperia Beta Program – also known as the Sony Android Concept Initiative.
STAMINA mode was introduced by Sony in 2013. It's a feature that can be described as the company's proprietary battery saving manager, designed to improve battery life by reducing background activities and allowing users to have more control over battery usage of various features. However, with the release of Android 6.0 Marshmallow, it appears that Sony has removed STAMINA mode in favor of Google's Doze mode, available on Android 6.0 natively. Much like STAMINA mode, Doze mode aims to improve and conserve battery life, but unlike STAMINA mode, Doze focuses primarily on reducing battery consumption when the smartphone is not in use. In other words, although the sole purpose of both STAMINA and Doze modes is to increase battery life, each one of these features approaches the task quite differently. It's also worth noting that, according to sources cited by XperiaBlog, STAMINA mode in Android 5.0 Lollipop appears to be more efficient than Doze mode in Android 6.0 Marshmallow.
According to Sony, STAMINA mode has been the most requested feature by users, and fortunately for Sony smartphone owners and fans of STAMINA mode, the feature has been confirmed to make a comeback in an unspecified future software release. As yet Sony doesn't have a release schedule for STAMINA mode, but the company claims that the feature "will be definitely available for members of the Xperia Beta Program in the near future".