From Forum Nokia Wiki

ID	TSS000316	Creation date	February 23, 2006
Platform	All Symbian	Devices
Category	Symbian C++	Subcategory	General

Keywords (APIs, classes, methods, functions):

Overview

SIS packages and localized resource files

Description

After adding multi-language support to an application by using localized resource files, the final step is to add them into a .pkg file and generate the SIS package.
There are two ways to do this: Resources can be added into a .pkg file either as language-dependent or language-independent files.
Language-independent files
These files are always copied to destination, regardless of language settings or user’s choices.
 "MyApp.r01" - "!:\system\apps\MyApp\MyApp.r01" ; 01=English
 "MyApp.r02" - "!:\system\apps\MyApp\MyApp.r02" ; 02=French
 "MyApp.r03" - "!:\system\apps\MyApp\MyApp.r03" ; 03=German
 ; etc (see TLanguage in e32std.h for all lang. enumerations)
The application framework decides which one to load during application startup, based on the current language setting. Copying all the resource files to the device will increase memory consumption, but on the other hand the application will follow the current language setting of the device (restart may be required).
Language-dependent files
Specifies a list of files, of which only one will be installed, depending on the language selected by the user during installation. The ordering and number of the files must match the languages that were specified in the languages line of the .pkg file.
    { "MyApp.r01",
      "MyApp.r02",
      "MyApp.r03" } - "!:\system\apps\MyApp\MyApp.rsc"
Since only one of the localized resource files is copied, the application cannot follow the language settings of the device. Changing the language of the application requires a reinstall.

Summary

The preferred method for installing resource files depends on the combined size of all localized resources and whether the application should be able to follow the language setting of the device.