Logging and Tracing for Using SAP JCo with VMC 
If you are using the SAP JCo in the Application Server with the Virtual Machine Container (VMC), you can access various log and trace files for error analysis.
Procedure
You can find the log and trace files in the following directories:
Trace Files
Locations (Java Logging API):
com.sap.conn.rfc
com.sap.conn.jco
Log Files
Category:
//System/Server/Connector/Rfc
You can change the settings for log and trace files in the file logging.xml (//<systemName>/cfw/conf/vmc_runtime/base/logging.xml).