how to use the submitChanges method ?

hello experts

in my project i am using the submitChanges method like below

	this.oModel.submitChanges({
		groupId: "addRequ",
		error: this.fnError.bind(this),
		success: this.fnSuccess.bind(this)
		
			});

the problem is that it is always generating the success method even when there are errors in the request

how to handle it please ?