The impact of this can be significant for users who depend on Citrix ADM for access to critical applications. This can happen if the license is expired, if the authentication server is down, or if the license is revoked due to a misconfiguration. In each of these cases, users will see the error message “Server is unavailable” when trying to connect to a server. We recommend that you check the status of all servers that host Citrix ADM before you start the upgrade to ensure that they are healthy. Following the upgrade, you may need to wait a few days before you can connect to these servers again.
Impact of license expiration. After upgrading to XenApp and XenDesktop 7.18, you may experience unexpected license expiration. This happens when an existing license is expired, but not yet revoked by Citrix. During the upgrade, Citrix ADM checks whether the license is still valid and not expired. If the license is still valid, Citrix ADM renews the license.
How to verify the accuracy of license expiration checks
To verify the accuracy of licensing checks, check the expiration date on the license. If you are upgrading to XenApp and XenDesktop 7.18 from a version earlier than 7.13, verify that your license is still valid.
Verifying or checking license validity: You can verify or check whether a Citrix ADM server is still active with the following command on each server:
Citrix ADM version> xaadm --license-status
Why does Citrix ADM require a license?
Citrix ADM is a infrastructure component of Citrix XenApp and XenDesktop. Citrix XenApp and XenDesktop require a license for each desktop that is managed. This license is granted when the user logs in to the server through an Active Directory domain, or a local database. If the user does not have a valid license, they will see the error message “Server is unavailable”.
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How to check the Citrix License Server status?
Citrix offers a tool to check the status of Citrix ADM. You can use this tool to determine if you have any Citrix licenses that are still valid and not expired.
Citrix License Server Status tool link: https://license-server.citrix.com/checkstatus
This tool gives you a list of all servers that host Citrix ADM, their status, and the number of days until the license expires. This allows you to quickly identify any servers that may be impacted after upgrading to XenApp and XenDesktop 7.18.
What to do if you see this error message?
If you see the error message “Server is unavailable,” we recommend that you check the status of all servers in your farm before you start the Citrix ADM upgrade. When your farm is upgraded, Citrix ADM checks all servers for existing licenses and renews them if they are valid. If any server has an expired license, Citrix ADM will stop processing new user connections until that license has been revoked by Citrix.
What to do if you see this error message: "Server unavailable"
Upgrade to XenApp and XenDesktop 7.18
The upgrade to XenApp and XenDesktop 7.18 has a few new features:
- Web Interface enhancements for published apps
- Single-Sign On improvements
- Auto remediation of license expiration issue
For the auto remediation of license expiration issue, Citrix recommends that you check the status of all servers hosting Citrix ADM before you start the upgrade to ensure that they are healthy. Login to the License Management Server and run "CitrixLicenseServer -status." If any of your servers are down, you can use this command to determine whether or not they are already in maintenance mode. If they are in maintenance mode, you will see a message on the console that says "Server is unavailable." The message is displayed at both logon and logoff. If it is not in maintenance mode, a message stating "Server is healthy" should be displayed during logon and logoff. After upgrading to XenApp and XenDesktop 7.18, you may need to wait a few days before you can connect to these servers again.