Frequently asked questions about Android BLE connection

I am using Nordic N51822 BLE for my android app, which works great when connected, but once connected, sometimes it automatically disconnects on its own. I couldn't figure out how to fix this.

I have connected the log between connected and disconnected. Please help me to fix this.

07-04 08:43:26.384 D/tecnogem connected running-->( 5675): yes
07-04 08:43:26.384 D/tecnogem synch running-->( 5675): rrrr
07-04 08:43:27.889 W/bt-btif ( 2401): bta_gattc_conn_cback() - cif=3 connected=0 conn_id=3 reason=0x0008
07-04 08:43:27.889 W/bt-btif ( 2401): bta_gattc_conn_cback() - cif=4 connected=0 conn_id=4 reason=0x0008
07-04 08:43:27.889 W/bt-btif ( 2401): bta_gattc_conn_cback() - cif=5 connected=0 conn_id=5 reason=0x0008
07-04 08:43:27.889 E/bt-btm  ( 2401): btm_sec_disconnected - Clearing Pending flag
07-04 08:43:27.892 W/bt-l2cap( 2401): L2CA_SetDesireRole() new:x0, disallow_switch:0
07-04 08:43:27.892 D/BtGatt.GattService( 2401): onDisconnected() - clientIf=5, connId=5, address=E8:60:71:E6:2B:94
07-04 08:43:27.893 D/BluetoothGatt( 5675): onClientConnectionState() - status=8 clientIf=5 device=E8:60:71:E6:2B:94
07-04 08:43:27.894 I/BluetoothLeService( 5675): Disconnected from GATT server.
07-04 08:43:27.898 D/BluetoothMapService( 2401): onReceive
07-04 08:43:27.898 D/BluetoothMapService( 2401): onReceive, action android.bluetooth.device.action.ACL_DISCONNECTED
07-04 08:43:27.905 D/BluetoothLeService( 5675): Trying to use an existing mBluetoothGatt for connection.
07-04 08:43:27.918 D/BtGatt.GattService( 2401): clientConnect() - address=E8:60:71:E6:2B:94, isDirect=false
07-04 08:43:27.919 D/BtGatt.btif( 2401): btif_get_device_type: Device [e8:60:71:e6:2b:94] type 2, addr. type 1
07-04 08:43:27.919 E/bt-att  ( 2401): device already in iniator white list
07-04 08:43:27.930 I/Coffee - BluetoothConnectionTracker( 2097): Bluetooth disconnection broadcast for H1-mini-I
07-04 08:43:27.930 I/Coffee - DevicePreferencesUtils( 2097): Failed to find BluetoothDevice.isEncrypted private API.
07-04 08:43:27.935 V/BluetoothFtpService( 2401): Ftp Service onStartCommand
07-04 08:43:27.935 V/BluetoothFtpService( 2401): PARSE INTENT action: android.bluetooth.device.action.ACL_DISCONNECTED
07-04 08:43:27.940 V/BluetoothSapReceiver( 2401): SapReceiver onReceive 
07-04 08:43:27.940 V/BluetoothSapReceiver( 2401): action = android.bluetooth.device.action.ACL_DISCONNECTED
07-04 08:43:27.941 V/BluetoothSapReceiver( 2401): Calling SAP service start service with action = null
07-04 08:43:27.944 V/BluetoothSapService( 2401): action: android.bluetooth.device.action.ACL_DISCONNECTED
07-04 08:43:27.945 V/BluetoothSapService( 2401): state: -2147483648
07-04 08:43:27.947 I/Coffee - BluetoothTrustlet( 2097): Device Micromax A74 is not allowed because it is either insecure or of unknown security and needs user confirmation
07-04 08:43:27.952 D/BluetoothDunService( 2401): parseIntent: action: android.bluetooth.device.action.ACL_DISCONNECTED
07-04 08:43:27.958 I/notification_cancel(  711): [1002,2401,com.android.bluetooth,2,NULL,0,0,64,8,NULL]
07-04 08:43:27.961 I/BTConnectionReceiver( 3389): onReceive(context, Intent { act=android.bluetooth.device.action.ACL_DISCONNECTED flg=0x4000010 cmp=com.google.android.googlequicksearchbox/com.google.android.search.core.service.BluetoothConnectionReceiver (has extras) }, [BluetoothDevice: address=E8:60:71:E6:2B:94, alias=null, name=H1-mini-I, majorDeviceClass=2304, deviceClass=2336]
07-04 08:43:27.963 I/notification_cancel(  711): [1002,2401,com.android.bluetooth,3,NULL,0,0,64,8,NULL]
07-04 08:43:27.964 I/BluetoothClassifier( 3389): Bluetooth Device Name: H1-mini-I
07-04 08:43:27.964 I/notification_cancel(  711): [1002,2401,com.android.bluetooth,8,NULL,0,0,64,8,NULL]
07-04 08:43:27.965 I/notification_cancel(  711): [1002,2401,com.android.bluetooth,151,NULL,0,0,64,8,NULL]
07-04 08:43:27.996 I/notification_cancel(  711): [1002,2401,com.android.bluetooth,-1000005,NULL,0,0,64,8,NULL]
07-04 08:43:27.996 I/notification_cancel(  711): [1002,2401,com.android.bluetooth,-1000006,NULL,0,0,64,8,NULL]
07-04 08:43:28.025 I/am_proc_start(  711): [0,6455,10096,com.skype.raider,broadcast,com.skype.raider/com.skype.android.audio.BluetoothReceiver]
07-04 08:43:28.025 I/ActivityManager(  711): Start proc com.skype.raider for broadcast com.skype.raider/com.skype.android.audio.BluetoothReceiver: pid=6455 uid=10096 gids={50096, 9997, 3003, 3002, 1028, 1015} abi=armeabi
07-04 08:43:28.054 I/am_proc_bound(  711): [0,6455,com.skype.raider]
07-04 08:43:28.102 I/LoadedApk( 6455): No resource references to update in package common
07-04 08:43:28.102 I/LoadedApk( 6455): No resource references to update in package com.cyngn.yu
07-04 08:43:28.102 I/LoadedApk( 6455): No resource references to update in package com.cyngn.yu
07-04 08:43:28.384 D/BluetoothGatt( 5675): readRssi() - device: E8:60:71:E6:2B:94
07-04 08:43:28.387 D/BtGatt.GattService( 2401): readRemoteRssi() - address=E8:60:71:E6:2B:94
07-04 08:43:28.388 D/BluetoothLeService( 5675): Trying to use an existing mBluetoothGatt for connection.
07-04 08:43:28.389 D/BtGatt.GattService( 2401): clientConnect() - address=E8:60:71:E6:2B:94, isDirect=false
07-04 08:43:28.389 D/BtGatt.btif( 2401): btif_get_device_type: Device [e8:60:71:e6:2b:94] type 2, addr. type 1
07-04 08:43:28.389 E/bt-att  ( 2401): device already in iniator white list
07-04 08:43:28.389 D/tecnogem connected running-->( 5675): no