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Member servers to ZDC communication

The ZDC will send an IMA ping to each MetaFrame server periodically to make sure that they are still alive. This happens by default every 60 seconds.The ZDC also requests a load level from a server if it has not received a load update for more that 5 mimutes.

Grace Period for Data Store and License Server


License Server will work normally with MetaFrame Presentation Server after the MetaFrame Server looses the connectivity to its Data Store. Even after 96 hours of Data Store failure, License Server still continues to work properly with those MetaFrame Presentation Server, which means it can check in and out licenses from the License Server’s license pool.


Licenses for MetaFrame Presentation Server are stored in License Server, so even if MetaFrame Server looses Data Store connectivity, it doesn’t affect any licensing activity.

For MetaFrame XP Family, licenses are stored in Data Store. Therefore, MetaFrame Server doesn’t function properly after the Data Store’s Grace Period (96 hours) expires.

The reason that there is no data store limit or grace period after PS3 is that prior to PS3 the licensing information for a farm was stored in the data store, which is why there was a 96hr grace period in the event of data store failure. When Citrix released PS3, they separated the licensing from the data store with a new licensing server. So from this point they kept the 96hr grace period, which only applied to the licence server. Apparently this grace period went to 30 days soon after due to customers complaining about the 96hrs not being sufficient to restore the license server and the fact that at the time the license server could not be made fault tolerant. 30 days grace period applies to license server being down, after which no new user connections can be made, and no limit on data store being down but you loose ability to manage farm.In this case LHC will come on the picture.

Points to remember:

  • Every 30 minutes, the IMA service contacts the central data store to see if anything has changed.

  • XenApp products connect with license server for every one hour.

  • If the data collector fails, existing and incoming sessions connected to other servers in the farm are not affected. The data collector election process begins automatically and a new data collector is elected almost instantaneously.

  • The data collector election process is not dependent on the data store.

  •  If the data collector goes down, sessions connected to other servers in the farm are unaffected.

  • If a data collector goes down, there is no single point of failure.

  • A primary domain controller or backup domain controller must not become the data collector for a zone.

  • If a new MetaFrame server joins the zone or the current data collector is unavailable then an election is triggered to determine a data collector.

  • Default time that inactive users will be logged off from the web interface is 20 mins in xenapp 5.0

  • Individual Presentation Server will continue to function for 30 days after it loses connectivity to a Citrix License Server.

  • Every five minutes the license server and the products send a heartbeat message to each other to verify that they are mutually communicating. (This is related to startup license)

  • Some Citrix products can operate in a disconnected mode (not connected to the server). These products allow a user to check out a license and operate the product for a preconfigured period of time that is set by the administrator. In this case, heartbeat messages are not exchanged. One example of disconnected mode is when a user checks out a Password Manager license for a laptop, and then uses the laptop when it is not connected to the server.

  • If for any reason, a Citrix product cannot contact the license server to request a license, the product goes into a grace period. This grace period is set by Citrix and differs depending upon the product.

  • During a license server connectivity outage, yes, you can reboot your member Presentation Servers, and yes, you can reboot your data collectors. The mps-wsxica_mps-wsxica.ini file will stay put as long as you don’t actively delete it.

  • If your environment includes a different directory service (such as Novell Directory Services for Windows) or you are a Citrix administrator without permission to manage Group Policy, use the Delivery Services Console to create policies for your farm.

  • In Active Directory environments, the farm GPO takes precedence over the local GPO on the server in the event policy settings conflict.However, Active Directory GPOs take precedence over the farm GPO.

  • If you are not seeing all the file types for your application this is because they may not yet be in the datastore. To pull the information from a server’s registry, right-click the server in the console select Other Tasks–>Update file types from registry. To pull FTA from all your servers right-click on the root of the farm and select Other Tasks –> Update file types. Bear in mind this is going to pull from all your server in the farm so if you have a large farm it may take a while.

  • Remember you must also configure Client Drive Mapping for Client to Server content redirection to work.

  • client to server redirection: update file types from registry.

  • server to client redirection: u can set it in policy.

  • If the license server is behind a firewall, you must assign a static port to the Citrix vendor daemon.

  • MS Access and SQL Express databases can only be accessed indirectly where you have the option when using MS SQL, IBM DB2 or Oracle.

  • The Farm Metric Server gets its information from the zone data collector, which is updated every 15 seconds by each MetaFrame XP server.

  • When a session is initialized, module.ini file is loaded and after the handshake with the server is over, the TSCAL license verification is made. If the license cannot be verified then the session just ends.

  • CmStart is responsible for launching the seamless engine which means no seamless windows without CmStart.exe in the AppSetup Key.

  • Every farm must have its own database or datastore.

  • altaddr is a command you run on the XenApp servers, not the web interface.

  • Memory optimization is based on the Citrix Virtual Memory Optimization service. This Windows service scans loaded DLLs every 10 seconds to determine which DLLs have been relocated. By default, this service runs under the context of the local system account but can be modified within farm properties.

  • If you get an error saying “An error ocurred while accessing the application”, check if server load is full and because of any policy, you get this error. Also check if your data collector is available or not.

  • Heartbeat is sent for every 5 mins from license server to its products .

  • Every half an hour IMA contacts data store to check if there are any changes so that it can update LHC.

  • ZDC will send IMA ping to each of its member servers for every 60 seconds. It also requests load if it doesnt receive load information for 5 minutes.

  • If license server down, xenapp servers runs for 30 days without any issues.

  • If data store down, xenapp servers runs for ever from LHC. we can reboot xenapp server also. Earlier version need a registry hack

  • Citrix advices a maximum of 25 zones

  • Zones are useful in traffic controlling.

  • Remember that each zone needs a data collector. First server added to a farm is data collector. from second server, election preference comes into picture.

  • When designing zones, the most important variables to consider are latency and bandwidth.

  • Citrix does not recommend having more than one zone in a farm unless it has servers in geographically distributed sites.

  • Citrix XTE server is for SSL Relay, Session Reliability and Password Manager Web Services. The name of the service for Session Reliability is ” Citrix XTE “. When you have any session reliability issues, restart XTE service and check.

  • The SSL Relay is a component that uses SSL to secure communication between Web Interface servers and server farms.

  • Every xenapp server will have xml service installed but the servers you add in WI only those server’s xml service uses xml broker for enumeration etc.

  • Make sure, you have 8083 port also opened in your license server in xenapp 7.X and higher.

ICA listener connection timeout

This setting specifies the maximum wait time for a connection using the ICA protocol to be completed. By default, the maximum wait time is 120000 milliseconds, or two minutes.

How many connections to servers in the farm can IMA process/keep at one time?

While there is no finite answer to this, there is a registry setting that limits the Host Resolver to keeping only 512 open connections to hosts. This is very important in large farm design, and it can be manipulated.

How does the ZDC keep track of all of the hosts in the farm to make sure they are live?

If ZDC does not receive an update within the configured amount of time from a member server (default 1 minute) in its zone, it sends a ping (IMAPing) to the member server in question.

How does the ZDC ensure servers communicating with are in the farm and authorized to trade information?

There are several layers of security used in this process, including those that exist in the Transport and Host Resolver functions. One of the most important checks a ZDC does to allow a server to communicate within the farm is called a magic number check. Magic Numbers are set the first time a server in a farm is joined into a farm.

Supported Clipboard Features:

1. Copy and paste of files between local workstation and sessions or between two unique sessions is not supported.

2. Drag and drop of either text or files between local workstation and sessions or between two unique sessions is not supported.

3. Copy and paste of text between local workstation and sessions or between two unique sessions is supported.

4. Copy and paste of files between two shared sessions is supported.

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