While starting the UPA Sync service, it remains in starting phase and we get
the following error in ULS logs -

OWSTIMER.EXE (0x04E4) 0x1390 SharePoint Portal Server User Profiles hyc6 High

Exception occured while connecting to WCF endpoint:
System.ServiceModel.ServerTooBusyException: The HTTP service located at https://servername:32843/f7d385690f414db0b5cee0da8d112e35/ProfilePropertyService.svc
is too busy. ---> System.Net.WebException: The remote server returned an
error: (503) Server Unavailable.
at System.Net.HttpWebRequest.GetResponse()

at
System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan
timeout) -
-- End of inner exception stack trace --- Server stack trace:

at
System.ServiceModel.Channels.HttpChannelUtilities.ProcessGetResponseWebException(WebException
webException, HttpWebRequest request, HttpAbortReason abortReason)
at
System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan
timeout)
at System.ServiceModel.Channels.RequestChannel.Request(Message
message, TimeSpan timeout)
at
System.ServiceModel.Channels.SecurityChannelFactory`1.SecurityRequestChannel.Request(Message
message, TimeSpan timeout)
at
System.ServiceModel.Dispatcher.RequestChannelBinder.Request(Message message,
TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannel.Call(String
action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[]
outs, TimeSpan timeout)
at
System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage
methodCall, ProxyOperationRuntime operation)
at
System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
Exception rethrown
at [0]:
at
System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg,
IMessage retMsg)
at
System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData&
msgData, Int32 type)
at
Microsoft.Office.Server.UserProfiles.IProfilePropertyService.GetProfileProperties()

at
Microsoft.Office.Server.UserProfiles.ProfilePropertyServiceClient.<>c__DisplayClass1.b__0(IProfilePropertyService
channel)
at
Microsoft.Office.Server.UserProfiles.MossClientBase`1.ExecuteOnChannel(String
operationName, CodeBlock codeBlock)

and

[ Date and Time ]  w3wp.exe (0x0AE4) 0x0EBC SharePoint Portal Server User
Profiles g11n High
UserProfileApplicationProxy.InitializePropertyCache:
Microsoft.Office.Server.UserProfiles.UserProfileException:
System.ServiceModel.ServerTooBusyException
at
Microsoft.Office.Server.UserProfiles.MossClientBase`1.ExecuteOnChannel(String
operationName, CodeBlock codeBlock)
at
Microsoft.Office.Server.UserProfiles.ProfilePropertyServiceClient.ExecuteOnChannel(String
operationName, CodeBlock codeBlock)
at
Microsoft.Office.Server.UserProfiles.ProfilePropertyServiceClient.GetProfileProperties()

at
Microsoft.Office.Server.Administration.UserProfileApplicationProxy.RefreshProperties(Guid
applicationID)
at
Microsoft.Office.Server.Utilities.SPAsyncCache`2.GetValueNow(K key)
at
Microsoft.Office.Server.Utilities.SPAsyncCache`2.GetValue(K key, Boolean
asynchronous)
at
Microsoft.Office.Server.Administration.UserProfileApplicationProxy.InitializePropertyCache()

--- Cannot get the application ID:

w3wp.exe (0x0AE4) 0x0EBC SharePoint Portal Server User Profiles d22b High
Failure retrieving application ID for User Profile Application Proxy 'URS Sourse
Test User Profile Service 2': System.NullReferenceException: Object reference
not set to an instance of an object.
at
Microsoft.Office.Server.Administration.UserProfileApplicationProxy.get_ApplicationProperties()

at
Microsoft.Office.Server.Administration.UserProfileApplicationProxy.get_AppID()

--- Cannot get_CurrentApplicationProxy:

w3wp.exe (0x0AE4) 0x0EBC SharePoint Portal Server User Profiles et8j High
UserProfileServiceUserStatisticsWebPart:LoadControl failed, Exception:
Microsoft.Office.Server.UserProfiles.UserProfileApplicationNotAvailableException:
This User Profile Application's connection is currently not available. The
Application Pool or User Profile Service may not have been started. Please
contact your administrator.
at
Microsoft.SharePoint.Portal.UserProfiles.AdminUI.ProfileAdminPage.get_CurrentApplicationProxy()

at
Microsoft.SharePoint.Portal.WebControls.UserProfileServiceStatisticsWebPartBase.LoadControl(Object
sender, EventArgs e)

Cause