https://devzone.nordicsemi.com/f/nordic-q-a/82417/ble---try-to-disconnect-during-sending-notificationHello, My config: - nRF SDK v17.1.0 - nRF SoftDevice S140 7.2.0 - FreeRTOS Kernel v10.0.0 (Amazon.com) My project used BLE connection with custom service (based on NUS). I am using nitifications for sendind custom data between my peripheral (serveren-USTelligent Community 13Mon, 06 Dec 2021 13:08:47 GMThttps://devzone.nordicsemi.com/thread/342070?ContentTypeID=1Mon, 06 Dec 2021 13:08:47 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5d5e3881-fc90-497a-93e4-3c2fb3a77d22Amanda Hsieh<p>Hi,&nbsp;</p> <p>Error 0x3401 is&nbsp;<a href="https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s130.api.v1.0.0/group___b_l_e___e_r_r_o_r_s___g_a_t_t_s.html#ga1d0833ac31d0c319e5286623b6301d0a"><span>BLE_ERROR_GATTS_SYS_ATTR_MISSING</span></a>&nbsp;which means&nbsp;<span>System attributes missing, use&nbsp;</span><a href="https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s130.api.v1.0.0/group___b_l_e___g_a_t_t_s___f_u_n_c_t_i_o_n_s.html#ga577c788e199b1a2c0d19602b07ef2515">sd_ble_gatts_sys_attr_set</a><span>&nbsp;to set them to a known value. See&nbsp;<a href="https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.s132.api.v7.0.1%2Fgroup___b_l_e___g_a_t_t_s___h_v_x___s_y_s___a_t_t_r_s___m_i_s_s_i_n_g___m_s_c.html">this</a>&nbsp;and&nbsp;<a href="https://devzone.nordicsemi.com/f/nordic-q-a/61014/getting-a-0x3401-ble_error_gatts_sys_attr_missing-from-sd_ble_gatts_hvx/248804#248804">this</a>.&nbsp;</span></p> <p><span>Also, have a look at this <a href="https://devzone.nordicsemi.com/support-private/support/280750/Is%20your%20peripheral%20using%20bonding?%20%20%20Devices%20that%20are%20bonded%20should%20store%20the%20CCCD%20state%20for%20the%20link%20between%20connections.%20This%20comes%20from%20the%20BLE%20specification.%20Is%20it%20an%20issue%20that%20it%20does?%20If%20so,%20it%20is%20the%20application%20that%20chooses%20whether%20or%20not%20to%20send%20any%20notifications.%20Perhaps%20you%20can%20stop%20the%20sending%20of%20notifications%20from%20the%20application%20if%20that%20is%20what%20you%20want?">case</a>.&nbsp;</span></p> <p></p> <p>-Amanda</p><div style="clear:both;"></div>