Value Mapping 
You can use value mapping to map the code values for customizing elements that are represented in the system to the code values of a named external list. The external list can be a global code list or a system-specific code list.
Prerequisites
You understand the meaning of the code values in the various systems and have agreed mappings with business users.
You have determined whether to use a global code list or a system-specific code list.
We recommend you use a global code list if you are using Enterprise Service Oriented Architecture (ESOA) communications or if target systems support value mapping.
You must use a system-specific code list if you are using Application Link Enabling (ALE) communications or if target systems do not support value mapping.
SAP target systems in releases EHP4 and below and non-SAP target systems can only support value mapping with the help of SAP NetWeaver Process Integration (PI) tools or other middleware tools.
Features
When implementing value mapping, you have the following options:
Use of a Global Code List (see Prerequisites section)
For more information, see Value Mapping: Use of Global Code Lists.
Use of a System-Specific Code List (see Prerequisites section)
For more information, see Value Mapping: Use of System-Specific Code Lists.