Memory In Android Phones - Sony Xperia T LT30p White Paper

Memory in Android phones

To use Android phones efficiently, users should be aware of the different types of phone memory. This
knowledge is important in order to understand, for example, where music, photos and videos are saved;
how many apps can be downloaded from Android Market; and how photos can be copied to a PC.
Generally, all Android phones share the same basic memory setup. What differs is how much memory is
available to you via the different types of memory, and whether your phone uses an external SD card or an
internal memory chip. Any information specific to the particular phone model described in this White
Paper is noted as such.
Please note that when internal memory is used, the figures you see in the phone information menus may
appear to not match with the total amount of stated physical memory. In other words, the figures might
not seem to add up. The reason for this is that some sections of the memory may use two memory cells
instead of one for every storage unit, in order to secure storage integrity. The need for such "double
storage" depends on the type of memory chips used and may therefore differ between products.
Types of memory
The types of memory described below are consistent with the terminology used in Sony mobile phone
menus and in other content relating to 2012 Xperia™ phones:
1. Dynamic Memory (also known as RAM, or non-persistent memory, because everything in RAM
disappears when the power is turned off) is used as "working memory" when the device is actually
running, and is shared between the operating system and all active applications and services.
Therefore, the amount of Dynamic Memory influences how many applications and operating system
services can run at the same time. In Android™ phones, the operating system automatically closes
applications and services that are not being used. However, such automatic functionality has limits.
For example, if a lower amount of RAM is assigned to a certain release of the operating system, phone
speed will be impacted.
If you experience problems with RAM, for example, if the phone runs slower than usual or if the Home
application restarts frequently when you leave an application, you should minimize the use of apps that
run all the time. Such apps could include, for example, applications that frequently download social
service updates. You could also consider using a static wallpaper instead of a live wallpaper.
To see which apps and services are currently active, go to Settings > Applications > Running
Services. You should have at least 50 MB, and ideally 100 MB or more, of free RAM to avoid
slowdowns and application restarts.
You should also be aware that if you update the phone to a later Android release, the load on the built-
in Dynamic Memory will increase due to the addition of more features. As a result, the phone may run
slower after an update.
All the memory types described below (in sections 2 to 5) together comprise "persistent" memory. What
this means is that all data and content stored on these sections of memory will "persist" after the power is
turned off (in contrast to the non-persistent RAM). Persistent memory can therefore be used for storing
applications, images, music and any other content which can only disappear after being explicitly deleted.
2. System Memory (also known as "System partition" or "/system") is used for the Android OS and for
most applications that are pre-loaded from the factory. This type of memory is normally locked, and
can only be changed through a firmware upgrade. There is usually some free space available in this
section of memory. However, since it is locked, you cannot save apps, photos or any other content to
this memory. System Memory is reserved for future firmware upgrades, which almost always need
more memory than the original firmware. You cannot see or influence the use of this memory.
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White paper | Xperia™ T
September 2012