Sharepoint Service Error: A deployment or retraction is already under way for the solution "xxx.wsp" , and only one deployment or retraction at a time is supported
Sometime this error has been occured from Windows SharePoint Services Administration command when the user do retractsolution or deploysolution like the follwing
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\BIN>stsadm -o retractsolution -name "%PackageName%" -local -url %TargetWebUrl%
or
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\BIN>stsadm -o deploysolution -name "%PackageName%" -local -allowGacDeployment -url %TargetWebUrl%
A deployment or retraction is already under way for the solution "xxx.wsp", and only one deployment or retraction at a time is supported
it occurs if anomalies deployment is running for the same package in the backend due to some previous deployment has been crashed before for some reason.
To avoid this problem do the followings:
Look for the deploy jobId to break the running by the following command:
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\BIN>stsadm-o enumdeployments
• Cancel the deploy typing the following command:
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\BIN>stsadm-o canceldeployment-id "GUID jobId"
• Check that deploy has been canceled by typing the following command:
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\BIN>stsadm-o enumdeployments
Hope it should work.