Even administrators may be unexpectedly absent for extended periods of time. If they do not have trained deputies, the continued orderly operation of the IT systems and applications they support will not be guaranteed. Administrators sometimes build up very extensive detailed knowledge about the IT systems and applications they oversee. This includes not only the products and solutions used, but special features of their operational environment and the specific configurations at hand. This knowledge enables administrators to quickly identify errors and implement requirements more easily. However, it often also means that complex IT systems and applications are administered by an individual person. If this person is absent, their knowledge is no longer available to the respective organisation.