How to fix SCCM HTTP Error 503 – The service is unavailable

Benoit LecoursSCCM11 Comments

Friday morning, the sun is shining, coffee is flowing… You monitor your SCCM site and find out that your WSUS Synchronization is failing when it was working perfectly yesterday. The first error that you encounter is SCCM HTTP Error 503 The service is unavailable in a couple of places:

  • In Wsyncmgr.log: 
    • Sync failed: The request failed with HTTP status 503: Service Unavailable. Source: Microsoft.UpdateServices.Administration.AdminProxy.CreateUpdateServer

SCCM HTTP Error 503

  • In Component Status : Monitor / System Status / Component Status
  • SMS_WSUS_SYNC_Manager is in a warning state:
    • WSUS Synchronization failed. Message: The request failed with HTTP status 503: Service Unavailable. Source:Microsoft.UpdateServices.Administration.AdminProxy.CreateUpdateServer

SCCM HTTP Error 503

  • If you try to access the URL for the WSUS Administration website (ex: http://SCCM2012:8530) it fails with the error: HTTP Error 503. The service is unavailable

SCCM HTTP Error 503

What cause SCCM HTTP Error 503 ?

Don’t panic, this issues can usually be fixed easily…but not that quickly. There are two main causes of this error:

  • The WsusPool Application Pool (in IIS) is stopped.
  • The Private Memory Limit (KB) for the Application Pool is not high enough (Default value 1843200 KB)

See detailed explanation of why this issue occurs, see the article written by Kent Agerlund.


The first thing you need to do is gives more memory to the WSUS Application Pool (WsusPool)

  • On your Software Update Point, start IIS Manager
  • Expand your site and click Application Pools
  • You’ll notice that the WSUSPool will be Stopped

SCCM HTTP Error 503

  • Select WsusPool in the center pane, and then click Advanced Settings in the Action pane

SCCM HTTP Error 503

  • In Advanced Settings, scroll to Private Memory Limit
  • Set the value to between 6 and 10 GB (in KB) and click OK

SCCM HTTP Error 503

  • Restart WsusPool by clicking Start and close IIS

SCCM HTTP Error 503


We will now initiate a Software Update synchronization in the SCCM Console

  • Go to Software Library / Software Updates
  • Right click All Software Updates and select Synchronize Software Updates

SCCM HTTP Error 503

  • Monitor the sync process in Wsyncmgr.log
  • Open Task Manager and monitor the IIS Worker Process memory consumption. It should go up to a couple of GB. If it reaches your memory limit, the pool will crash again. Give more memory to the WsusPool and restart the synchronization

SCCM HTTP Error 503

Be aware that the initial synchronization could take a couple of hours. Be patient and be sure to apply Kent’s recommendations to avoid this to occurs again in the future.

11 Comments on “How to fix SCCM HTTP Error 503 – The service is unavailable”

  1. Pingback: Software updates indepth in SCCM | satishappv

  2. Pingback: Updates sync failed with “Sync failed: The request failed with HTTP status 503: Service Unavailable. Source: Microsoft.UpdateServices.Administration.AdminProxy.CreateUpdateServer” | SCCM PEEK

  3. Hi

    I have the same problem but wsus pool service is running I have restarted it and private memory is set to 0. I am planning on removing and re-installing SUP. Anyone has any other ideas please

  4. Thank you so much,
    Nearly re-installed WSUS with the Software update point as I was getting Error 505 when trying to connect to the http://WSUSserver:Port as well as an error on the WSUS console itself.
    All our services was running under the IIS application pool, but increasing the memory did the trick.
    Restarted the WSUSpool and everything started to work.

  5. Since this was before patch Tuesday for anyone that reads this and is having issues with their WSUS/SCCM and clients not checking correctly. There is a large update this month, at least for 1511, that hoses WSUS and client check-in. KB4019473 x64 to be exact was the issue, it is a little over 1GB in size and once it was declined in WSUS clients started checking in fine about 10-15 later. Prior to doing this my SCCM box was consuming over 80% of both CPU and RAM with client requests.

    I will be deploying the msu file via a package in SCCM to go out with the other patches that were pulled down.

  6. Pingback: How to fix SCCM HTTP Error 503 |

Leave a Reply