CommunicationException A specific extension of the Runtime OperationFailedException that is thrown when the host application is unable to communicate with the remote User Directory. 
CrowdRuntimeException CrowdRuntimeException is the superclass of Crowd-specific exceptions that may be thrown but not necessarily caught. 
GroupNotFoundException Thrown when the specified group could not be found. 
MembershipNotFoundException Used to denote that a particular USER-GROUP or GROUP-GROUP membership does not exist. 
OperationFailedException Thrown when an operation failed for some reason. 
UserNotFoundException Thrown when the user is not found.