I have a custom Visual Studio workflow. There are hundreds of instances of it running in a site collection. I now need to update it. The workflow consists of some custom task forms and the workflow itself and I have WSP files built for all of these.

Should I use Install-SPSolution or Update-SPSolution so that the existing instances of the workflow keep running without being affected by the update?

2 Answers 2


Update-SPSolution is what you need, assuming you did not add any new features to the workflow. If you did, you need to use Install-SPSolution

Check out this link referencing upgrading workflows: https://msdn.microsoft.com/en-us/library/aa543659.aspx

In both, the DLLs and the files will be updated in the GAC the same way, but if the solution has changed the ID of a feature, changed scope of a feature, changed version of a feature, changed elements.xml, or has a new Property element to the Feature.xml file, then a complete retraction and reinstall will have to be performed--remove the workflow solution and remove it from the farm entirely before Installing.

  • could you explain the difference between Update-SPSolution & Install-SPSolution with regard to what happens to the DLL's in the GAC? Apr 27, 2015 at 13:39
  • @motionpotion see my edit.
    – Mike
    Apr 27, 2015 at 13:47
  • In the case where a complete retraction & redeployment happens then the running instances of the workflow will stop because the existing version of the DLL will no longer be available in the GAC? Apr 27, 2015 at 14:50
  • Workflows that are running should stay intact with the old definition. Check out this thread: social.msdn.microsoft.com/Forums/sharepoint/en-US/…
    – Mike
    Apr 27, 2015 at 18:56
  • But if the old WSP is retracted then does that remove the old versions of DLL's for the workflow & custom approval forms? Thus meaning the running instances cannot find the DLL version in the GAC? This is what is not clear to me. Apr 27, 2015 at 19:00

Updating the work flow's wsp is little shady. You can use the Update-spsolution to upgrade it but what about the running instance of the Workflow? and it also depend what you change in the wsp.

Check this for more information.

Upgrade custom workflow in SharePoint

  • this doesn't give me a definitive answer to the question. The running instances must stay working in my case. Apr 27, 2015 at 16:16

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