This is the first operation that must be invoked during an ArcGIS Server upgrade. Once the new software version has been installed and the setup has completed, this operation will be available. A successful run of this operation will complete the upgrade of ArcGIS Server. This operation is available only when a server machine is currently being upgraded. It will not be available after a successful upgrade of a server machine.
If errors are returned with the upgrade operation, you must address the errors before you may continue. For example, if you encounter an error about an invalid license, you will need to re-authorize the software using a valid license and you may then retry this operation.
A flag to indicate if the operation needs to be run asynchronously. The default value is false.
Values: true | false
The response format. The default response format is html.
Values: html | json | pjson
Below is a sample POST request for upgrade:
POST /webadaptor/admin/upgrade HTTP/1.1 Host: machine.domain.com Content-Type: application/x-www-form-urlencoded Content-Length:  runAsync=false&f=json
JSON Response example