Abstract: Disclosed is a method, apparatus and a computer program of a virtual execution environment. In one aspect thereof a data processor includes a read-only storage medium and a virtual machine monitor configured to execute a program in a virtual container. Prior to execution of the application a set of application components accessed during a phase change are recorded in the read-only storage medium in a manner predetermined to minimize the time needed to retrieve the set of components. At the occurrence of the phase change, or prior to the occurrence of a phase change if the files are prefetched, the virtual machine monitor retrieves the components from the read-only storage medium. In a further aspect thereof there is provided a packager of an application to be executed in a virtualization environment by a virtual machine monitor.

Abstract: A method and computer system for determining an existence of a file and, possibly, information related to the file are provided. The method and system include providing a file name, generating a file designator from the file name, and generating a hash value from the file name. The hash value is used to index a cache containing other file designators that meet a certain criterion, and if no entry is found in the cache, an operating system call is performed. If an entry is found in the cache, the entry of the cache is compared with the generated file designator. If the entry and the generated file designator are not the same, an operating system call is performed. If the entry and the generated file designator are the same, this indicates that the criterion is satisfied.