Check the below setting
1) check configtool-> secure store -> connection string -> listener port number
2) check /oracle/SID/112_64/network/admin/listener.ora and tnsnames.ora
3) check /usr/sap/SID/SYS/profile/oracle/tnsnames.ora
Listener port number should be same in all above location if you are running ABAP + JAVA engine Like Solman. In case of change of port number JAVA engine may not be connected to DB because of wrong listener port number.