App-V Sequencer is a wizard-based tool administrators use to create Microsoft Application Virtualization-enabled applications. The sequencer produces the application ―package, which consists of several files. These files include a Microsoft Application Virtualization-enabled application (.sft) file, one or more Open Software Description (.osd) "link" files, one or more icon (.ico) files, a manifest xml file which can be used to distribute Application Virtualization-enabled applications with Electronic Software Delivery (ESD) systems and a Microsoft Application Virtualization project (.sprj) file. The .sft, .osd, and .ico files are stored on App-V Management Server; these files are the keys that the App-V client uses to access and run Microsoft Application Virtualization-enabled applications.

What is sequencing?

Conceptually, sequencing is a lot like packaging in the traditional ESD sense. But the term “sequencing” doesn’t really describe the process well enough. When we think of packaging, we think of creating a set of files and configurations that will later be installed automatically on a client. In this sense, it’s all about installing the application (most of the time without user input).

Sequencing is really about executing the application. By installing the application into the SoftGrid Sequencer, you are creating not only the application package but also its virtual environment, and determining how it will be streamed to the client. Instead of trying to package the application for installation, you go through the basic installation of the application (into a virtual environment) and then into an execution phase where you actually run the application in the virtual environment.

The trick with sequencing is to capture what files the application normally would install (and in what order these files are loaded at execution time) and determine what is needed OUTSIDE the application that will be placed in the virtual environment for it to execute

Sequenced applications perform as if they are installed on the local machine when launched by users. A sequenced application does not alter the underlying operating system because each application runs in a virtual environment and is isolated from other applications that may be installed or running on the client. This isolation dramatically reduces application conflicts and decreases the required amount of pre-deployment testing. Because applications are hosted on the Virtual Application Servers and streamed to clients, fewer installations and upgrades are necessary thereby reducing the cost of application support and deployment.

The Sequencer monitors the installation and setup process for applications and records all the information necessary for the application to run in the virtual environment. This process also determines which files and data are applicable to all users and which information users can customize.

The key activities of producing a package?

Figure: The key activities of producing a package

During sequencing, the Sequencer walks you through the process of Installation, Launch, Customization, and Save phases of the application.

The first phase in the process is the Installation phase - During the installation phase, you specify the package name and an optional associated comment that will be associated with the package. You can also configure advanced monitoring options during this phase. Advanced monitoring options include specifying the block size and whether you will install automatic updates during monitoring. The sequencer records all necessary information and configurations required to create a virtual application package and the associated file and registry settings.

Launch phase - During the launch phase, you can specify any required file associations and security descriptors that should be configured with the package. You should open the application as many times as necessary to ensure application functionality and stability. 
 

Figure: A walkthrough and brief description of the different steps of the launch phase

Customization phase - During the customization phase, you can configure your package by using the associated .osd files. You can specify whether any associated scripts should run inside or outside of the virtual environment, specify additional actions that should be performed, specify how associated scripts run (synchronously or asynchronously), and specify any additional scripts that should be run under the user context.

Save phase - During the save phase, all required files for the virtual application package are created. The files created are .sprj, .sft, .osd, .ico, .xml manifest, and the Windows installer (.msi) file.

A good example is Microsoft Excel. In Excel, you would most likely select something in the File menu, and then maybe add some text and numbers into the spreadsheet, and maybe even add an equation. This tells the Sequencer that it needs to first download the minimum components required to launch the application, and then send down the files (or parts of the files/code blocks) that it needs to perform these functions. These will become the first parts of the application in SEQUENCE to be sent to the client. This allows the users to use the application as fast as possible without waiting for the entire application to stream to the desktop.