SAP In-Memory database requires the replication of data from a source system. There are three methods of data replication from source system to SAP IMDB.
If your source is ERP system then SAP recomments using SAP Landscape Transformation (SLT) Replcator. Source can also be non-SAP system. As name suggests it updates HANA system using database triggers.
While connecting to SAP source system Replication Server uses remote function call (RFC) network communication channels and for non-SAP source system it uses database connection. SAP HANA system and SAP LT Replication Server uses database connection for communication.
You don’t need new hardware (server) for SAP LT Replication Server if the source system is SAP. It can be installed in same source system (SAP source system) if the configuration is good. In case of non-SAP source system we do need separate system and database connection is used as network communication channel.
Extraction Transformation Load (ETL) Based Replication:
It uses SAP BusinessObjects Data Services 4.0 to load data from any source other then ERP (Non-SAP source system).
Transaction Log Based Data Replication (Sybase Replication):
It is based on database log files. It captures table changes from log file. This replication method is only recommended for customers that have been invited to use this technology during the RTC of the SAP HANA 1.0 product delivery.