Problem: When you running a Process Chain in BW system, you saw an error RSBOLAP018: Java system error, as shown below.
Investigate: Check log as shown in the error description. You will find this line on files defaultTrace.xx.log :
ERROR RSBOLAP (018): Java system error: An Unknown Error Occured During Portal Communication
MSGV1: An Unknown Error Occured During Portal Communication#
How to find log location is described in my previous post .
Solution : Check your Portal connection from Java to ABAP, ABAP to Java. If the connection is configured properly, so you can retry to execute a process chain again. Why? This issue is explained more detail in SAP Notes 916090 – RFC error messages in Web Application Designer 2004s. For short description is the process chain needs an active and valid connection during most of the operation. So this could be caused by a network glitch or broken connection which impact on Portal connection error.