First of All Lets make few things clear

• Independent Management Architecture (IMA) is now called as Flexcast Management Architecture (FMA).
• CItrix Studio Is replacing the Citrix Service Delivery Console which means there will be Single console for all your Tools like PVS,MCS,Citrix xenapp, Xen Desktop, Store Font,Netscalar.
• Storefront  is new Name of Web Interface. that actually enables Citrix now to Support HTML 5 for Various Devices like PC,Laptop,Mobile, Tablet’s and Also its hold Session based cache which enable user to provide Shortcut of most used application as per his Preference, And Like Always its Has Improved Performance & Look.
• Session Lease – Remember there is no LHC in citrix 7.6  Hence Connection leasing enables users to connect and reconnect to their most recently used applications and desktops, even when the Site database is not available. The connection leasing feature supplements the SQL Server high availability best practice
• Delivery Controller — The Delivery Controller is the central management component of any XenApp or XenDesktop Site
• Database — At least one Microsoft SQL Server database is required for every XenApp or XenDesktop Site to store all configuration and session information. This database stores the data collected and managed by the services that make up the Controller. Install the database within your data center, and ensure it has a persistent connection to the Controller.
• Virtual Delivery Agent (VDA) — The VDA is installed on each physical or virtual machine in your Site that you want to make available to users.
• Receiver — Installed on user devices and other endpoints, such as virtual desktops, Citrix Receiver provides users with quick, secure, self-service access to documents, applications, and desktops from any of the user's devices, including smartphones, tablets, and PC
• Director — Director is a web-based tool that enables IT support and help desk teams to monitor an environment.
• License server — License server manages your product licenses. It communicates with the Controller to manage licensing for each user's session and with Studio to allocate license files
• Hypervisor — The hypervisor hosts the virtual machines in your Site could be Vmware,Xenserver, Hyper-V
• Provisioning Services — Provisioning Services is an optional component of XenApp and XenDesktop available with some editions. It provides an alternative to MCS for provisioning virtual machines. Whereas MCS creates copies of a master image, Provisioning Services streams the master image to user device. Provisioning Services doesn’t require a hypervisor to do this, so you can use it to host physical machines. When Provisioning Services is included in a Site, it communicates with the Controller to provide users with resources.
• NetScaler Gateway — When users connect from outside the corporate firewall, this release can use Citrix NetScaler Gateway (formerly Access Gateway) technology to secure these connections with SSL. NetScaler Gateway or NetScaler VPX virtual appliance is an SSL VPN appliance that is deployed in the demilitarized zone (DMZ) to provide a single secure point of access through the corporate firewall. but if you want get familiar with netscalar please Read in my blog for netscalar in label’s
• Citrix CloudBridge — In deployments where virtual desktops are delivered to users at remote locations such as branch offices. certrainly it compresses and Encrypt the data I/O, it mainly used in reduce the WAN link traffic
• Machine catalogs : its collection of machines
• Delivery Groups are collections of users given to access a common group of resources
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• Machine Creation Services (MCS) — A collection of services that create virtual servers and desktops from a master image on demand, optimizing storage utilization and providing a virtual machine to users every time they log on. Machine Creation Services is fully integrated and administered in Citrix Studio.
  
• Provisioning Services — Enables computers to be provisioned and reprovisioned in real-time from a single shared-disk image. Provisioning Services manages target devices as a device collection. The desktop and applications are delivered from a Provisioning Services vDisk that is imaged from a master target device, which enables you to leverage the processing power of physical hardware or virtual machines. Provisioning Services is managed through its own console.
  
• Existing images — Applies to desktops and applications that you have already migrated to virtual machines in the data center. You must manage target devices on an individual basis or collectively using third-party electronic software distribution (ESD) tools.

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for the Step By Step process, Please Refer the Articles in concern Labels of the Blog

How to Perform Migration of Citrix ?

Question TIME NOW

Q: Does connection leasing allow users without a current session to connect to Citrix apps while the database is down?

A: Yes.  The delivery controller will keep a list of previous connections from the user. Those previously used connection parameters will be used in the future if the database is unavailable. The default timeframe is 2 weeks, but this can be modified with PowerShell. Leo Singleton wrote a great blog on the ins and outs of connection leasing.

Q: Is the local text echo functionality part of XenApp 7.6?

A: HDX has been enhanced over many years to improve upon the responsiveness and interactivity of the user session, something Local Text Echo did but in a slightly different manner. So Local Text Echo, as it was in 6.5, is not part of 7.6, but HDX includes interactivity enhancements that make the need for Local Text Echo obsolete.

Q: How much RAM should one give to the “Cache in RAM with overflow to disk” feature for XenApp 7.6?

A: Any amount will be a benefit.  I’ve seen 1, 2 and 3GB of RAM allocated per VM show significant value to a XenApp VM resulting in IOPS of less than 1 per user. Read more on Overflow to disk for XenApp on my blog on ‘Changing the read/Write Ratio for XenApp’

Q: What license do I need for XenApp vGPU sharing feature?

A: Available for Enterprise and Platinum. Please reference the following feature matrix http://www.citrix.com/go/products/xendesktop/feature-matrix.html

Q: Are there real numbers on the database size?

A: Yes, these values haven’t changed much since this release:http://support.citrix.com/servlet/KbServlet/download/36246-102-707006/XenDesktop%207%20Database%20Sizing_v4.pdf

Q: When migrating (not rebuilding), does the XenApp server have IMA and FMA running at the same time?

A: No.  When you are ready to migrate a XenApp 6.5 worker to the XenApp 7.6 site, the upgrade wizard will remove the 6.5 worker from the farm, uninstall the 6.5 software and install the 7.6 VDA while placing the server into the 7.6 site.

Q: Is there a difference/risk in using the migration tool over doing a rebuild of the farm (assuming that the underlying operating system isn’t changing)?

A: Migrating the farm and policy settings via the migration tool is just a time saver, especially for large, complex environment.  As for the XenApp workers, many people prefer to rebuild in that it is an opportunity to refresh the server back to a clean state (assuming you aren’t using something like PVS for image management). The benefit of the upgrade wizard for the workers is that you don’t have to go through the app install/configuration again.

Q: What steps must I do to upgrade from Version 7.5 to 7.6 and in which steps?? License Server? Delivery Controller? Storefront? Director? VDA’s? What is the right order?

A: Please refer to this document for detailed steps http://support.citrix.com/proddocs/topic/xenapp-xendesktop-76/xad-upgrade.html

Q: If my policies are stored in Active Directory instead of XenApp, do I need to run the Policy Export utility?

A: No, the export/import is only for Farm stored information. For AD policies, you will continue to use them

Q: Does the import farm utility also include application icons?

A: Yes.  The icons are exported and imported as part of the migration utility

Q: Does the migration utility work for XenApp 6?

A: Yes, although it is experimental. The commands used to gather the farm, policy and application settings from XenApp 6.5 are the same in XenApp 6.0, but the migration utility has not been tested nearly as in-depth as XenApp 6.5.

Q: In XenApp 6.5, if we launch two different apps that are both hosted from the same server, it only creates 1 session. Is this still the case in 7.6?

A: This is called session sharing and it does work in XenApp 7.6

Q: Can be VDA installed on Windows 2003 server?

A: No, the VDA is only supported on Windows 2008R2 SP1, 2012, 2012R2, 7 SP1, 8 and 8.1

Q: How do we enable that Provisioning Services RAM Cache feature that conserves IOPS for XenApp 6.5 environments?

A: You need to upgrade to the latest Provisioning Services version and your XenApp 6.5 servers must be managed by Provisioning Services.

Q: Are mixed domain environment supported with XenApp 7.6?

A: Yes. Many different type of complex Active Directory deployments are supported, as can be seen from this article: http://support.citrix.com/article/CTX122417

Q: Is App-V required for XenApp 7.6 if I would still like to stream my applications like I did in XenApp 6.5?

A: Yes. Application Streaming that was part of XenApp 6.5 has been replaced with Microsoft App-V.  XenApp 7.6 includes integration with App-V to simplify publishing and integration.

Q: I’m already on XenApp 7.5.  Is it worthwhile to go to XenApp 7.6?

A: You will want to review the following page (http://www.citrix.com/products/xenapp/whats-new.html) as well as the webinar on What’s New in XenApp 7.6. Once you are on XenApp 7.x, the upgrade process is easy in that you can do in place upgrades on a component-by-component basis.  So you can have 1 controller on 7.6 and another on 7.5 while your VDAs are on 7.5.  This allows you to take your time for doing the upgrade instead of doing a big band type deployment.

Q: We are on XenApp 4.5 and are deciding on upgrading to 6.5 or 7.6.  Which version would you recommend?

A: As XenApp 4.5 is a Window 2003 solution, you are correct that the time to upgrade is now.  I would recommend you move to the latest Windows operating system (2012R2), which will give you the longevity over anything else.  Plus, if you start with XenApp 7.6, you won’t have to think about the upgrade from 6.5 to 7.6.

Q: When is XenApp 6.5 end of life?

A: All XenApp product lifecycle dates can be found here: http://support.citrix.com/article/CTX122442

Q: If we have a multiple geographical location deployment of XenApp 6.5 utilizing zones, does this mean we will need to implement delivery controllers, SQL servers, etc at each location?

A: Assuming those geographical locations are not connected with a low latency connection, then yes, you will have a XenApp site at each location.  Depending on the size of those sites, this might be beneficial as this will allow you to build smaller failure domains, as each site is independent, a fatal error at one site will not bring down another site.  However, for XenApp 6.5 deployments with many small zones of only a few servers each, if you are unable to consolidate into a single data center, you will want to remain on XenApp 6.5 for the time being.

Q: Can a XenApp 7.6 site include Windows 2008 and 2012 servers?

A: Yes. Based on the new FMA architecture you can have a single site using Windows 2008R2, Windows 2012 and 2012R2.

Q: What happens if one of the delivery controllers goes offline? Is there a service failure?

A: No. In XenApp 7.6, all delivery controllers within a site are Active-Active.  If you recall, in XenApp 6.5 and previous versions, you have a Zone Data Collector, and if that data collector fails, a new one will be elected, which also might be hosting apps.  This has caused performance issues if not configured correctly.  This risk is no longer relevant in XenApp 7.6

Q: If I upgrade to XenApp 7.6 from 7.5, do I have to upgrade StoreFront?  Do I have to upgrade Web Interface to Storefront?

A: No. You can stay on your current version. However, there might be a situation where a new feature in XenApp will not work with an older component or you won’t be able to use a new StoreFront feature.

Q: What file do you use to configure the StoreFront App Aggregration feature?

A: Located here: C:\inetpub\wwwroot\Citrix\storename\web.config, where “storename” is the name of your store. Also, make a backup copy of your web.config file before modifying.

Q: With regards to the database, what information is there on High Availability?

A: For high availability, please reference the following article:http://support.citrix.com/proddocs/topic/xenapp-xendesktop-76/xad-plan-high-availability.html