1. A method for managing life-cycles of a software as a service software application, comprising: installing the software as a service software application in a system landscape on a computer server, the system landscape containing at least an application server and a database server; separating system data for the software as a service software application from customer data of a plurality of customers for the software as a service software application and storing the system data and customer data in different databases, wherein customer data is stored outside of the system landscape and customer data is decoupled from system data by replacing copies or links to system data within the customer data with one or more system independent placeholders; creating a virtual machine image for the system landscape, the virtual machine image to include the databases containing system data and exclude the databases containing the customer data; deploying the software as a service software application to one or more computer servers by loading virtual machines on one or more computer servers based on the virtual machine image; and when the software as a service software application is to be upgraded to a new version, preparing a new virtual machine image with the new version of the software as a service software application and deploying the new version of the software as a service software application by loading virtual machines on the one or more computer servers based on the new virtual machine image.