The guideline refers to availability parameters for technical products, systems or system components. In a comprehensive definition of the term, the availability of a technical product is determined by certain parameters of survivability, maintainability, logistics and usage-side organization or the influencing variables and influencing conditions that can be assigned to these. On the basis of this general definition, a selection of parameters is described in more detail that have proven to be useful under certain conditions for indicating the availability of technical systems within the framework of development, procurement, support or usage programs.*www.vdi.de/ 4004