Operation
App-V Application Virtualization is composed mainly of two components – SystemGuard and App-V Sequencer. SystemGuard tracks and analyzes configuration repositories and resources used by the application and intercepts the use of these resources, redirecting them to the virtualized instances of the resources. Virtualized resources include virtualized data such as user profile information and data; virtualized system services, such as COM controls, windows services and copy/paste abilities; and virtualized configuration repositories like registry hives and INI files. Not all applications that run as a service can be virtualized, although these limitations may change in future product versions. The virtualized instances are created in the runtime sandbox which hosts the virtualized instance, representing the resources of the actual client system the application is being executed on. Thus the application is decoupled from the resources of the system the application is installed on. Each application, or multiple instances of the same application, is run in its own virtual sandbox, each with its own set of virtual resources. The SystemGuard runtime environments can include specific dependencies such as DLL files as well. Multiple SystemGuard runtime environments can be in execution simultaneously.
App-V sequencer is the component which packages an application for virtualization and streaming. It analyzes the application for the resources that it requires and creates the SystemGuard runtime environment that it will require. It also packages specific DLL files that it might require at the client side. It then packs all the application code and data into App-V's proprietary format that makes it more suitable for streaming. Individual libraries are packed separately so that each library can be streamed as required, rather than having the client to download the entire application at the beginning. Most importantly, the sequencer translates file and registry references into user, machine, and operating system neutral references. This often allows limited portability of sequenced applications between OS versions.
At the client, when a streaming request is made to an App-V server, portions of the entire sequencer package are transferred to the client, who unpacks and initializes the SystemGuard environment and hosts the application inside it (with System Center Configuration Manager and the stand-alone client, the entire package contents are transferred). Each package is cached by the client for the duration of the application session. User settings are stored in the local system itself.
Virtualized application packages can also locally reside at the client computer, thus eliminating the need of application server and streaming. Microsoft Systems Management Server can be used to push these packages to the client computer in the absence of a virtual application server. In this scenario, the App-V SMS Connector can be used to locally manage the application packages.
Read more about this topic: Microsoft App-V
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