A method of operating an information technology system and information technology system

The information technology system (10) comprises at least a first (CM) and a second processing unit (SM). The first (CM) and the second processing unit (SM) are formed into a common execution of an application program. The first processing unit (CM) and the second processing unit (SM) is in each case an installation routine (suc1, SUC2) is assigned, which is designed to control an update of a first and a second program part of the application program. Depending on a state of the respective installation routine (suc1, SUC2) and dependent on a respective update progress of the first and the second part of the program during an update of the application program is the first processor means (CM) is a current state from a predetermined set of possible states associated with and second processing unit (SM) a second actual condition. After restarting the system (10) or as soon as a successful storage of the first program part and the second part of the program, or an error in storing the first program part and / or the second program part is detected, become dependent (of the actual state of the first processing unit CM ) and the actual state of the second processing unit (SM) is performed in each predetermined processing steps in a predetermined order from the first (CM) and the second processing unit (SM).