Random Access Memory; Volatile File Storage (Cache Disk); Persistent Storage; Application Folder - Symbol MC909X Integrator Manual

8 - 10 MC909X Integrator Guide

Application folder.

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Random Access Memory

Executing programs use RAM to store data. Data stored in RAM is lost upon a warm boot. RAM also included
a volatile file storage area called Cache Disk.

Volatile File Storage (Cache Disk)

Windows Mobile 5.0 memory architecture uses persistent storage for all files, registry settings, and database
objects to ensure data is retained even after a power failure. Persistent storage is implemented using Flash
memory technology which is generally slower than volatile RAM memory. In certain situations the speed of the
operation is more important than the integrity of the data. For these situations, Symbol has provided a small
volatile File Storage volume, accessed as the Cache Disk folder. Disk operations to the Cache Disk folder are
much faster than to any of the persistent storage volumes, but data is lost across warm boots and power
interruptions. Note that a backup battery powers RAM memory, including the Cache Disk, when you remove
the main battery for a short period of time.
The mobile computer uses the Cache Disk for temporary data that can be restored from other sources, for
example, for temporarily "caching" HTML web pages by a browser or generating formatted files to send to a
printer. Both situations benefit from the increased speed of the cache disk, but you can restore the data if
needed.
DO NOT use the Cache Disk as a method to improve application performance. Analyze applications that
perform slower in persistent storage to optimize disk access. Common areas for optimization include
minimizing the number of reads and writes to a file, removing unneeded debug logging, and minimizing file
flushing or closing files.

Persistent Storage

Windows Mobile 5.0 protects all data and applications from power-related loss. Because Windows Mobile 5.0
mounts the entire file system and registry in persistent storage (rather than using RAM), MC909X devices
provide a reliable storage platform even in the absence of battery power.
Persistent storage provides application developers with a reliable storage system available through the
standard file system and registry APIs. Persistent storage is optimized for large reads and writes; therefore,
applications reading and writing data in large chunks tend to outperform those applications reading and writing
small blocks of data. Data in persistent storage is lost upon a clean boot.
Persistent storage contains all the directories under the root directory except for Application, Cache Disk, and
Storage Card (if a storage card is installed). Persistent storage is approximately 60 MB (formatted).
Application Folder
The Application folder is a super-persistent storage that is persistent even after a clean boot. Accessing data in
the Application folder is slower than accessing persistent storage. The Application folder is used for
deployment and device-unique data. For example, network profiles can be stored in the Application folder so
that connection to the network is available after a cold boot. The Application folder is approximately 20 MB
(formatted).