java.lang.UnsupportedOperationException

I am using Windchill PDMLink Release 11.0 and Datecode with CPS M030-CPS08

PersistenceHelper.manager.delete();

객체 삭제 하면서 발생하는 에러.

Here are the errors that I faced
INFO : wt.system.err wcadmin - wt.util.WTException: java.lang.UnsupportedOperat
ionException
INFO : wt.system.err wcadmin - ?? ??: java.lang.UnsupportedOperationException
INFO : wt.system.err wcadmin - at wt.fc.collections.UnmodifiableCollect
ions$UnmodifiableIterator.remove(UnmodifiableCollections.java:895)
INFO : wt.system.err wcadmin - at java.util.AbstractCollection.retainAl
l(AbstractCollection.java:410)
INFO : wt.system.err wcadmin - at wt.projmgmt.StandardProjMgmtService$3
.notifyVetoableMultiObjectEvent(StandardProjMgmtService.java:552)
INFO : wt.system.err wcadmin - at wt.events.StandardKeyedEventBranch.in
tDispatchEvent(StandardKeyedEventBranch.java:298)
INFO : wt.system.err wcadmin - at wt.events.StandardKeyedEventBranch.di
spatchVetoableMultiObjectEvent(StandardKeyedEventBranch.java:263)