About SharePoint with 16+ Cores

Well, If you update .Net 4.7.2 or higer it is OK, otherwise it is a bad idea.

More speficially,
ReaderWriterLockSlim with reentrant have design limitation which can lead serious performance down for previous .Net versions. And Sharepoint pretty much depended on this thread syncronization object. Specially Blob Cache and ObjectCache wraps and using them. More CPU causes more thread contention, excesive locking thats brings slowness.

Example callstacks:
SPReaderWriterLock named [BlobCache] waited 43992 milliseconds to acquire lock. Call stack:
at Microsoft.Office.Server.Utilities.SPReaderWriterLock.AcquireLock(Boolean readerLock, Boolean upgradable, Boolean throwException)
at Microsoft.Office.Server.Utilities.SPReaderWriterLock.AcquireLock(Boolean readerLock, Boolean upgradable)

Microsoft_Office_Server!Microsoft.Office.Server.Utilities.SPReaderWriterLock.AcquireLock(Boolean, Boolean)
Microsoft_Office_Server!Microsoft.Office.Server.ObjectCache.SPCache+MossObjectCache.UpdateUsageMap(System.String, UInt32, UInt32)
Here are some threads about the problem.

These issues has been fixed with .Net Framework 4.7.2 version!.

Pls check .NET Framework 4.7.2 Release Notes

Again don’t think about 64cpus makes more performance. It depends of the software boundaries/limitations and several other things..
My suggestion, scale up with multiple machines. It is more cheaper and stable. ! Not with excessive hardwares. (8 cores are fine 🙂 )

If you have that monster machines, don’t worry you can  use it with HyperV and scale up VMs.


SharePoint User A authenticated as User B

How could that happen ?

Let me give a some information about the problem:

Intermittently Users authenticated with reverse proxy, impersonate incorrectly and User A may become User B . Based on user privileges , end users experiencing either access denied or having different user identity and permissions.


  • 1 In the middle Device ,who redirects authentication or re-authenticate. (I am not meaning a hacker device , if you are using SSL, it is not possible easily but your system admins can). It is mostly a Reverse Proxy configured officially by your system admins.All most every modern proxy has a feature that uses Port Sharing or Re-use Session functionality. It is perfectly fine , provides high performance , prevent reauthentication and port exhaustion problem.It is works for well almost every scenario . Almost!!!
  • Session-Based Authentication , (Like NTLM or Certificate Authentication). In our scenario,We have one web application with two Authentication Provider , 1 for default CBA/NTLM and 1 for CBA/Form-Based Authentication. (Issue happens on CBA/NTLM part)
    • This configuration provides another authentication layer on SharePoint ,and force SharePoint to use Federated Authentication mechanizm , so you will see Fed Auth cookies are in use.

Some important information:

Federated Authentication over CBA/NTLM. Despite the fact that it is a token/cookie based architecture, it is depending on NTLM authentication under the cover. It means it is still a Session Based Authentication.

Why we have a problem:
Because Any middle device setting for “same TCP session re-use” is not suitable/unsupported for any “Session Based” authentication type.

The issue, It is not related directly SharePoint implementation , It is related that how the Session Based Authentication works.

Also same problem may occur ; faulty middle device software and other incorrect configurations.

How the issue happens,
Lets have a look in details for Federated Authentication over CBA/NTLM.

In TCP/Network Layer – We don’t have any authentication in this layer.
We have two end points . Point A (Reverse Proxy) to Point B (SharePoint WFE)
Before autentication a TCP connection estabilishes between that two points.

Point A – IP , Source Port : 45000  -> Point B – IP : port 443
We are now calling this “A TCP Channel” or “A TCP Session” .

After TCP connection is estabilished then HTTP start to work in that channel.

HTTP Layer
User go to the server anymously first , the server provides authentication challanges it supported. And user provides its credential assets . This is called NTLM Handshake;


TCP Channel should not closed until NTLM handshake complete. It is a requirement for
NTLM authentication . Thats why , all modern web servers , use a standart/feature called HTTP Keep Alive which provides “Persistent Connection” not only NTLM handshake duration , also several requests are handled in same TCP Channel until Client or Server close the connection.


After NTLM HandShake completed , IIS Stores the Session Information ,
TCP Channel  X  -> [Point A]  [IP], [Port] <=> Identity : Authenticated User A.  (Or Anonymous)

(If we don’t use , HTTP Keep Alive,  For every request we need to do re-authenticate . (it is not a session based authentication it is called Request Based Authentication . Well NTLM fails in that scenario. You will see flooding 401 responses on NTLM handshake.)


Now SharePoint come in the scenario , It builds claims and tokens on IIS/NTLM Identity , creates the tokens via Security Token Service , caches the tokens with Distributed Cache or Local Cache.

SharePoint and IIS believe and trust , underlayer TCP Session belong to only one verified authenticated identity.

If you have more than one authentication provider , SharePoint also builds Federated Authentication Cookies , default 5 days duration .Cookie – Token pairs must be match for user verification.
Fed Auth Cookie sent to client with last response in NTLM handshake (Status 200 or 302).
and corresponding Token has been cached in server (default 10 hours).

All incomming requests are considered valid/authenticated based on Fed Auth Cookie – Security token pair.

What happens if SharePoint can’t find token in the cache:
If the cookie valids , It rebuilds the token  and cache the token again and updates the cookie.  (You will have another 5 days, “sliding” )
It do not re-authenticate.

What happens if the Cookie expires: Well you need to reauthenticate.

What happens if the TCP Channel closed : you need to reauthenticate. Even client send close channel , in the middle devices can prevent it. Because It wants to reuse that TCP Channel.

So far so good,

But what if someone , some other user  use the same TCP Channel and send requests to the server . Well exactly what is happening if the reverse proxy does in session-reuse functionality.

SharePoint and IIS believe and trust , underlayer TCP Session belong to only one verified authenticated identity.Because how the bible says for Session-Based Authentication works.

Problematic Scenario:
Lets assume User A authenticated , have a valid cookie and continue communication without re-autheticate using Cookie-Token pairs for validation.

In mean while User B make a request (anonymous first) from same TCP Channel and requesting authentication.It is NTLM.  Well the TCP Channel is not closed , it is the same channel,  There is no possibility to understand it is the different user, Server reuthenticate the user.

After NTLM HandShake completed , IIS Stores the Session Information by overriding ,
TCP Channel  X  -> [Point A]  [IP], [Port] <=> Identity : Authenticated User B.  (Or Anonymous)
IP is the always Reverse proxy it isn’t changed.Also we have using the same TCP Channel so the port also same. It is absolute override.

Now the channel is belong to USER B instead of USER A.
Well User A still have no issues, he has a valid cookie and we have a valid token , so User A and User B communicates with the server without any problem in same tcp channel.

But the problem happen when the token is missed/expired (default 10 hours) .
What SharePoint does , verify the channel in that point ,ask to the IIS what was the Identity  ? IIS tells : it is UserB . SharePoint recreates the token and updates the cookie for UserB in a request which belong to UserA.
Now User A gets inccorect cookie and have inccorect token cached . It becomes User B by now.

Depends on permissions , either facing access denieds or have access UserB’s resources.

This problem is called “Session Hijacking“.
This is not a security hole in Sharepoint ,IIS or NTLM .

An anology :
Lets assume , you have a internet faced web site under authentication have must protected resources and if you enable anonymous access on that server in same resources .Is it considered security hole in authentication mechanizm or your code ? Of course not.

Well, there is still a security issue because of unsupported or incorrect configuration . Also it is not depended on Sharepoint, It may happen any ASP.NET application on any kind of Session-Based Authentication.

In conclusion,

Any “Session Based” authentication (like NTLM, Certificate auth etc.)  to work needs one TCP Channel per authenticated user.

SharePoint Federated Authentication for Claims Based Authentication over NTLM is depending on the underlying NTLM Authentication. NTLM is a session based authentication . Any middle device setting for “same TCP session re-use” is not suitable/unsupported for these type of authentications.


  • Disabling “TCP Channel/Session re-use” feature in middle devices
  • Update in the middle devices firmware for any faulty software
  • Not using Session-Based Authentication with Reverse Proxy “Session re-use” feature or changing authentication type for any/suitable “Request-based” authentication or “token based” authentication (like ADFS) or Form based authentication.

Note: Don’t mess with “Session ” that is TCP level Session/Channel, not an application level session object or structure !! (OSI Layer 5)

Clean draft versions via PowerShell

SharePoint versionining is very cool feature, but in time or setting incorrect version limitations can cause performance issues. When this happen you may want to get rid off older draft versions.

Following script is cleans for older draft versions in a library while keeping all major versions. Also you can keep defined number of last major items drafts available.
Note: This script doesn’t delete any major item.

# .\CleanDraftVersions.ps1 -siteUrl <Site Url> -webName <webName> -listName <ListName> -versionsToKeep <Number> -delete=<$true|$false>
# -siteUrl : Url of the Site Collection
# -webName : Specific subsite (leave empty for root web)
# -listName : Specific ListName
# -versionsToKeep: Number of major item’s drafts will be preserved (including current version)
# -delete : $false (default) for reporting only ,$true for deleting.
# Highligts: Red will be deleted , Yellow will be preserved , Green current Item .

# .\CleanDraftVersions.ps1 -siteUrl “http://contoso.com&#8221; -webName “” -listName “Pages” -versionsToKeep 10 -delete $false


After updating SharePoint 2013 to November 2017 CU or later you may not be able to open documents with Office


This issue mostly happens if you update your sharepoint from command-line by using psconfig.exe and when you miss the correct parameters.

PSConfig.exe -cmd upgrade -inplace b2b -wait -cmd applicationcontent -install -cmd installfeatures -cmd secureresources -cmd services -install

Thanks to Rodney for excellent work to detecting the issue .we have an easy workaround of this.But we don’t like much to copy/paste dlls around.

Instead of manullay copy/paste the stssoap.dll around bin folders and if you already run psconfig.exe by missing applicationcontent -install parameters , you can use following powershell commandlet ;

for more information about PSCONFIGUI.EXE and PSCONFIG.EXE please read outstanding article by my colleague Stefan Gossner

Mainstream support for SharePoint 2013 will end in 6 months

Mainstream support for SharePoint 2013 will end on April 10th, 2018:

After this date only security fixes will be provided for SharePoint 2013. Regular hotfixes can no longer be requested.

If not already done we recommend to start planning the migration to SharePoint Server 2016 as soon as possible.

mapping with destination attribute ‘name’ has a source attribute marked as export-only

Recently I have faced an issue with MIM 2016 and SharePoint 2016 while exporting string (Multi-Value) from SharePoint to AD.

Well , i will not go in detail for MIM and SharePoint 2016 configuration for export operations . There are articles around , if you interested :
please check:

So the reproduce the issue;
I have create a User Profile Property as string (Multi-Value) from User Profile Service-> Manage User Properties. That was the easy part . (Please notice i didn’t select any TermSetId when i creating the property)

We need to “Refresh Schema” of the Management Agent for SharePoint (SPMA) to discover newly created property .Well it succeeded without issue. But there is a problem , when you export the schema.xml of the SPMA you will notice that property marked as “Export-Only” .

dsml:attribute ref="#Rooms" required="false" ms-dsml:isAnchor="false" ms-dsml:allowedOperation="ExportOnly"

Thats means you can not import from SharePoint to Metaverse that property . (It is working in contrawise , Export for SPMA means Metaverse to SharePoint , Import means SharePoint to Metaverse)

So it will not allow you to create “Attribute Flow” other direction (Import) in SPMA Properties. I have faced a very definitive error that is “EXPORT-ONLY”

So i have tried to mitigate this by modify SPMA schema xml . “Export Management Agent then modify the xml and get rid of dsml:allowedOperation="ExportOnly" , and again update management agent with new xml. But no luck.
Well it is worked at the beginning and i able to export my value to the AD until when i need to “Refresh Schema” for SPMA . I have faced following error in event viewer.

“BAIL: MMS(10132): ..\cdext.cpp(416): 0x80070057 (The parameter is incorrect.)
BAIL: MMS(10132): ..\xstack.cpp(405): 0x80070057 (The parameter is incorrect.)
BAIL: MMS(10132): ..\xparse.cpp(436): 0x80070057 (The parameter is incorrect.)
BAIL: MMS(10132): ..\iafparse.cpp(2423): 0x8023050e (The import attribute flow rules XML defines an invalid/incomplete rule.): IAF: mapping with destination attribute ‘Rooms’ has a source attribute marked as export-only
BAIL: MMS(10132): ..\xstack.cpp(540): 0x8023050e (The import attribute flow rules XML defines an invalid/incomplete rule.)
BAIL: MMS(10132): ..\xparse.cpp(544): 0x8023050e (The import attribute flow rules XML defines an invalid/incomplete rule.)
BAIL: MMS(10132): ..\iafexec.cpp(141): 0x8023050e (The import attribute flow rules XML defines an invalid/incomplete rule.)
ERR_: MMS(10132): ..\mastate.cpp(12497): Error creating import attribute flow rules object: 0x8023050e
BAIL: MMS(10132): ..\mastate.cpp(12585): 0x8023050e (The import attribute flow rules XML defines an invalid/incomplete rule.)
BAIL: MMS(10132): ..\mastate.cpp(6263): 0x8023050e (The import attribute flow rules XML defines an invalid/incomplete rule.)
BAIL: MMS(10132): ..\ma.cpp(670): 0x8023050e (The import attribute flow rules XML defines an invalid/incomplete rule.)
BAIL: MMS(10132): ..\ma.cpp(928): 0x8023050e (The import attribute flow rules XML defines an invalid/incomplete rule.)
Forefront Identity Manager 4.4.1302.0”

After hours of investigation noticed that it is related with  TermSetId in Profile DB.
I have checked and compare the properties in the database and noticed if  i create a multi-value string even without termset id it is storing an emty guid inside ,well the other properties was null. So I have done a manuel set NULL (which is not supported) to test. Voila , now i can able to refresh schema again and everithing works fine. But this is not a valid resolution . It is not supported . And what if i want to use Term Set Id with that Profile Property   ?

Luckly it was resolved by SharePoint team long time ago . But not documented any where or i didn’t find it.

SharePoint connector (build 4.3.2036.0 or higher) have a new setting .Enabling the new setting “Import auto-updated attributes” on the Connectivity tab of the SharePoint Connector allows us to import an attribute that has a TermSetID other than NULL.


It was also resolve my issue with Multi-Value string without TermSetId (even so it has a empty guid it is not NULL) .

Outgoing emails are not working in SPS2016 after Security Update May 2017

This article has inform you previously there may be some concequences after May 2017 Security Update for SharePoint in some special configurations.

There is a security update May 9,2017 for SharePoint Server 2016
You can find details in following KB

Well it is confusing, as you may know, out of the box mail configuration for SharePoint always anonymous. Thats correct.
But in some special configuration applied by customers to force SharePoint processes (w3wp or owstimer) to authenticate with their identities to Exchange server;  If aspnet:AllowAnonymousImpersonation settings was disabled for Authenticated users (well it doesn’t work for anonymous users at all) it may work.

<add key=”aspnet:AllowAnonymousImpersonation” value=”false” />

More details explained for this.
Security Warning : Well the suggested action for this settings , this should be enabled. Otherwise anonymous request will have higher rights with Application Pool Identities does.

The problem of this kind of authentication is incorrect ,not expected  for SharePoint and Microsoft considered this is a Security Issue. As Microsoft said by design it has to be anonymous. With that Security fix will prevent this. SharePoint will be always use anonymous authentication through SMTP servers.

For customers who interested force authentication , well there’s no way to disable the anonymous-only behavior but we have valid workaround for that:

  1. If you are using Exchange, you can set up a separate receive connector configured as externally secured, and restricted to the IP addresses of the SharePoint server(s) in their environment.  This will allow SharePoint to send e-mails anonymously through this receive connector, but the connector will treat the e-mails as if you were authenticated.  All other SMTP clients will continue using the regular receive connectors and any authentication policies associated with those receive connectors.
  2. Set up a smarthost SMTP relay that will accept e-mails anonymously from the SharePoint server(s), and then relay them to the company’s SMTP infrastructure using authentication.