Oracle Application Server: How to change the name of the instance

Just replace the actual name in the following files 

• ias.properties
• opmn.xml 
• sysman/emd/targets.xml
• webcache.xml

Change the instancename there and restart the opmn.

opmnctl stopall
opmnctl startall

Be aware of the report server instance name, which is another thing, with another changing procedure.