สงสัยเรื่องการใช้ OleDBDataAdapter.Update() ค่ะ เหมือนจะเข้าใจอะไรผิดไป?

Function Coupon_INSERTCouponLog(ByVal eventID As Integer, ByVal EPCouponTable As DataTable) As String
        Dim strInsertCmd As String = "INSERT INTO tbLog( couponPKID,eventID,userID,userName,gamenickname,usergender,usedcoupon,tradestatus,playdate,createdate,haverandomflag,iswinner) VALUES(@CouponPKID," + eventID.ToString() + ",@UserID,@UserName,@GameNickname,@UserGender,@UsedCoupon,1,@CreateDate,getdate(),0,0)"

        Dim dbm As LuckyDBManager = New LuckyDBManager()
        If Not dbm.ConnectToDB() = "SUCCESS" Then
            Return Nothing
            Exit Function
        End If

        Dim succ As String = "SUCCESS"
        Dim dbTrans As OleDb.OleDbTransaction = dbm.dbCon.BeginTransaction()
        Try
            Dim cmdInsert As OleDb.OleDbCommand = New OleDb.OleDbCommand(strInsertCmd, dbm.dbCon, dbTrans)
            cmdInsert.Parameters.Add("@CouponPKID", OleDb.OleDbType.Integer, 4, "couponPKID")
            cmdInsert.Parameters.Add("@UserID", OleDb.OleDbType.Integer, 4, "userID")
            cmdInsert.Parameters.Add("@UserName", OleDb.OleDbType.VarChar, 20, "username")
            cmdInsert.Parameters.Add("@GameNickname", OleDb.OleDbType.VarChar, 20, "gamenickname")
            cmdInsert.Parameters.Add("@UserGender", OleDb.OleDbType.VarChar, 10, "usergender")
            cmdInsert.Parameters.Add("@UsedCoupon", OleDb.OleDbType.Integer, 4, "usedcoupon")
            cmdInsert.Parameters.Add("@CreateDate", OleDb.OleDbType.Date, 8, "createdate")

            Dim insertAdapter As OleDb.OleDbDataAdapter = New OleDb.OleDbDataAdapter()
            insertAdapter.InsertCommand = cmdInsert
            insertAdapter.Update(EPCouponTable)

            'success
            dbTrans.Commit()
        Catch ex As Exception
            succ = "ERROR"
            HttpContext.Current.Response.Write(ex.Message)
            dbTrans.Rollback()
        Finally
            dbm.ConnectionClose()
        End Try

        Return succ
    End Function