Monitoring and Error Handling in the SAP Gateway 
This documentation will help administrators to monitor the gateway and to analyze and solve errors.
Integration
For information about the architecture of the gateway see Architecture of the SAP Gateway.
For information about the administration of the gateway see Administration of the SAP Gateway.
Features
Depending on the type of the instance in which the gateway is running, you have various tools available to monitor and administrate the gateway.
Gateway monitor in SAP GUI (transaction SMGW, in AS ABAP only)
Gateway monitor at operating system level (program gwmon .exe)
SAP Management Console (runs in the Web browser)
SAP MMC (Windows)