Defining Logical Systems 
You use this function to decide to which other clients (in your system and in external systems) you want to have an RFC connection for the Postprocessing Office.
Note
You only need to execute this function if you want to use the Postprocessing Office across all clients or systems. Each client that you want to connect is identified by a logical system For more information, see Cross-System Processing.
Prerequisites
You have set up the logical systems for which you require RFC connections. For more information on setting up logical systems, see SAP Customizing under 
SAP NetWeaver 
Application Server IDoc Interface / Application Link Enabling (ALE) Basic Settings 
in the section on Setting Up Logical Systems or see the SAP Library under IDoc Interface / ALE.
Procedure
Specify the appropriate logical system for all systems and relevant clients that you want to connect.
Example
You are using the software components Account Management (FS-AM) and Loans Management (FS-CML) in two different logical systems KBICLNT500 and AENCLNT000. Both software components use the software component SAP Business Partner for Financial Services (FS-BP). This means that both systems may contain postprocessing orders for the business partner object type. To display and edit the postprocessing orders for the business partner object type for Loans Administration from Account Management, define the logical system AENCLNT000.
Note
This example applies only if the business partner master is synchronized in the different systems.