A method of performing tasks on a production computer includes retrieving a one task description file stored on a task computer and containing a description of a task on a production computer, transferring the task description file from the task computer to a production computer, causing the production computer to check that the file is associated with at least one task stored on the production computer, performing the task associated with the file in the production computer using the file, if the association check was successful, wherein the task computer has open ports and the production computer keeps the ports closed so that access by a user of a first user group to the task computer is arranged, but access by a user of the group to the production computer is prevented while steps above are performed in a predetermined operating state of the production computer.