Configuring WSMAN Limits

As you probably know by now, all of PowerShell remoting is done via streaming extensions to WSMAN.  WSMAN is the SOAP-based DMTF standard protocol for managing everything.  As you explore the limits of what you can do with WSMAN or PowerShell remoting, you may encounter errors like this:

[7592:0]PS> New-PSSession
[localhost] Connecting to remote server failed with the following error me
ssage : The WS-Management service cannot process the request. This user is
allowed a maximum number of 5 concurrent shells, which has been exceeded.
Close existing shells or raise the quota for this user. For more informat
ion, see the about_Remote_Troubleshooting Help topic.
    + CategoryInfo          : OpenError: (System.Manageme….RemoteRunspa
   ce:RemoteRunspace) [], PSRemotingTransportException
    + FullyQualifiedErrorId : PSSessionOpenFailed

What is going on here is that we put in a number of default constraints into the system to protect your systems from accidental misuse.  We didn’t want a beginner PowerShell user writing a script which accidentally consumed all the resources on your servers.  We can’t protect against everything but we spent some time thinking about the common mishaps and put some default guardrails in.  

I like the story (it might even be true :-) ) about software controls on some of the fighter jets.  The SW developers knew what the design limits of the planes where so they wrote the control software so that it wouldn’t exceed the capabilities of the plane.  The pilot’s reaction was, “we’d only be pushing the plane to that degree when the other alternative was getting shot down – I’d rather risk having the wings tear off then being guaranteed to get shot down.”  So while we put in guardrails, we also put in the ability to move those guardrails.  Look, they are your machines.  You are smart people.  You often know more than we do.  We allow you to make decisions which may be great and may hurt yourself.   (NOTE: In my opinion we set some of the Maximum’s too low.  We may reevaluate some of these in the future on the grounds of general principles but let me know if you have any concrete situations where the maximums are too small.)

If you want to change the controls, all you have to do is to CD into the WSMAN: drive and the LOCALHOST subdirectory and change things.  It’s as easy as this:

PS> cd WSMan:\localhost\Shell
PS> dir

   WSManConfig: Microsoft.WSMan.Management\WSMan::localhost\Shell

WARNING: column “Type” does not fit into the display and was removed.

Name                      Value
—-                      —–
AllowRemoteShellAccess    true
IdleTimeout               180000
MaxConcurrentUsers        5
MaxShellRunTime           2147483647
MaxProcessesPerShell      15
MaxMemoryPerShellMB       150
MaxShellsPerUser          5

PS> Set-Item .\MaxShellsPerUser 25

It is worth spending a little bit of time exploring the WSMAN drive and what you can do with it.

To find out more about the drive and what the values mean do the following:

PS> Get-Help WSMAN

PS> Get-Help About_WSMAN

<Update – not all the settings are documented there.  The full list is available HERE >


Jeffrey Snover [MSFT]
Distinguished Engineer
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