When more than 1 user uses Simulator in Datamapper builder, the datamapper
builder crashes and the trace reports the following error :
ERROR  :20070607:09.56.46.43:r4edi(tool_toolbox(DMbuilder)):SOCKET_NGET:
peer has closed down connection
ERROR
:20070607:09.56.46.43:r4edi(tool_toolbox(DMbuilder)):SIM_HIERCHMSGENV.GETREPLY:
lost connection to processing engine

Problem is due to the duplication of ports in the services file. That means 2 entries with same port numbers but 2 different port names.
Also Increasing  the sysman pool in your service file and adding it to the porter pool inside task manager will improve the performance.