A system, method and computer program product for allocating shared resources. Upon receiving requests for resources, the system determines whether there are any pending updates for a VM image for provisioning a virtual machine (VM) for the request. For each image with pending updates the system determines whether to replace the stored image with an updated VM image and provision from the replacement or, update a single instance of the image and provision from the single instance. The system also determines an optimal time to update images with pending updates. After replacing an image, the system provides an alert indicating that an updated said VM was provisioned.