The data model used for all Z-Stack projects, by default, copies constants into XDATA (RAM) during initialization. This reduces the amount of RAM that is available for application purposes. For most applications, this does not present a problem. Most constants used in Z-Stack are located in XDATA and should not be changed by the user. Constants are placed in XDATA by omitting any data space declaration or by using the keyword __xdata. NOTE: TI only recommends the solutions outlined in this document if it is not possible to locate all necessary constants in XDATA. When a project uses pointer types that differ from the default type, the user can expect a loss in performance. All constants that a project uses will be located in the NEAR_CODE segment by the linker. Therefore, it is possible to run into a situation where a small or medium size project (i.e. 100k of code) will fail to link because there is not enough space in the NEAR_CODE segment. The developer should take this into account and avoid using too many constants.

http://www.ti.com/lit/swra104