{
        "REQUEST" : {
                "op" : "update",
                "args" : {
                        "updates" : [
                                {
                                        "q" : {
                                                "_id" : ObjectId("530fadb98e0e468e10a335f7"),
                                                "x" : {
                                                        "$xyz" : 1
                                                }
                                        },
                                        "u" : {
                                                "a" : 1
                                        }
                                }
                        ]
                }
        },
        "RESPONSE" : {
                "ok" : 1,
                "nModified" : 0,
                "n" : 0,
                "writeErrors" : [
                        {
                                "index" : 0,
                                "code" : 65,
                                "errInfo" : {
                                        "causedBy" : [
                                                {
                                                        "index" : 0,
                                                        "code" : 2,
                                                        "errmsg" : "unknown operator: $xyz"
                                                },
                                                {
                                                        "index" : 0,
                                                        "code" : 2,
                                                        "errmsg" : "unknown operator: $xyz"
                                                }
                                        ]
                                },
                                "errmsg" : "multiple errors for op : unknown operator: $xyz :: and :: unknown operator: $xyz"
                        }
                ]
        }
}