What Is Local Host Cache?

In previous post I wrote about what will happen if the Citrix XenApp farm lost connection with its datastore. Well, because of Local Host Cache, users will still be able to access the applications without too much issue. But, what is Local Host Cache (LHC)?

LHC is like a mini-DB of the farm, and created on all Citrix XenApp servers. Why I said mini-DB? It is because it contains a portion (subset) of Data Store information. 


There are 4 main information stored in the LHC :

• All servers in the farm, and their basic information.
• All applications published within the farm and their properties.
• All Windows network domain trust relationships within the farm.
• All information specific to itself. (Product code, SNMP settings, licensing information)

There are 2 primary functions of LHC :

• Redundancy - a Citrix XenApp still function as normal if connection to datastore losts.
• Performance - LHC cache information used by ICA clients for enumeration and application resolution. By having this, a faster response to ICA client request is provided, as the server does not need to contact other member servers about published applications.

LHC info is stored in Imalhc.mdb (an Access database). By default, it is stored in %ProgramFiles%\Citrix\Independent Management Architecture folder.

IMA service is heavily related to LHC. IMA service is responsible to get LHC synchronzied with the data store. Hence, restarting IMA service during DB server outage will cause the service can't be started.



Reference :

• http://careerride.com/view.aspx?id=2774
• http://support.citrix.com/article/CTX759510

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What Happen If My XenApp Farm Cant Connect to the Data Store?

This is one of my favorite interview question, I just don't know why. it seems simple, but some candidates failed to give a proper answer (poor them). I wish all of them better luck next time.

Okay, now back to the real business. From Citrix Administrators Point-of-View, losing a DB may cost chaos, depending on how severe the issue is. However, from user perspective, nothing is different. Users wont really impacted of this. They still be able to launch Citrix published applications and works as normal. Thanks to Local Host Cache (LHC), it eases the burden of Citrix Admins (oh really?)

However, although all Citrix XenApp servers have LHC, there are some conditions that Citrix Admins need to remember :

• There is no grace period for this (MPS 3.0 and above). Users still be able to connect to the Citrix farm (lucky!)
• Only static information  available to users. No new info can be added and current info cannot be changed (not really...)

In any circumstances, DO NOT :

• Restart / reboot the Citrix XenApp servers. it will cause the server to contact DB server. This will result IMA service won't started.
• Restart IMA service (same reason as above).
• Re-create LHC (in order to re-create LHC, we need to stop IMA service).

Reference :

• http://citware.blogspot.com/2012/05/if-you-loose-connectivity-to-data-store.html
• http://citrixsolutions.blogspot.com/2009/04/all-about-local-host-cache.html
• http://support.citrix.com/article/CTX105763

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Error on Citrix Web Interface - Credential Error

This time, I want to discuss on an error occurred when users want to access Citrix Web Interface. This may happen for new farms or when new XML servers added to the farm. 



Issues :

• Users received below error when accessing Citrix Web Interface :
  

Troubleshooting 

1. From Citrix Web Interface server, go to application log, and search for Event ID 31003 and Event ID 30110.
2. Those Event IDs indicates that XML service transition failed.

   
   

   Event ID 31003 in Application Log

   
   

   

   Event ID 30110 in Application Log

   
   
3. Check which server(s) is/are configured as XML Service servers for the farm, and RDP to the server(s). 

Resolution :

1. go to Start > run, type regedit and press Enter.
   
   
   
   
   
2.  browse to HKLM\Software\Citrix\IMA
   
   
3. Add a new registry value (ensure it is DWORDS (32-bit) Value)
   
   
4. Set the name as UseNetworkLogon
   
   
   
   
   
   
   
5. Right-click at the newly created key, and click Modify...
   
   
   
6. Change the value data to 1. Ensure the base is Hexadecimal.
   
   
   
7. This is the final outcomes :
   
   
   
8. Go to Services, and restart Citrix Independent Management Architecture service.
   

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XTE Service Cannot be Started

Citrix XTE Server service is one of the essential service in Citrix XenApp. it is directly relates to Session Reliability. What is Session Reliability? Please read from here and here. Is Session Reliability Goood? Hmm, read this article and go figure it out. (such a lazy bum of me, huh?)

It might occurred in your environment that XTE Server service can't be started at one server, while the rest are fine. Session Reliability option is enabled from Citrix Console.  So, what's next?  

Issues :

You may received below error when you want to start XTE Server service.

 

Troubleshooting 

browse to %programfiles%\Citrix\XTE\Conf, check whether file httpd.conf is existed / is there any content inside the file.

Resolution :

1. Copy the file from server that is working fine. 
   
   

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How To Auto-Create and Configure ctx_cpsvcuser

As mentioned in previous post,  ctx_cpsvcuser can be created and configured with a tool, but it is limited to certain Citrix XenApp versions only :

• Feature Pack 1 for Presentation Server 4.5
• Presentation Server 4.5 for Windows Server 2003
• Presentation Server 4.5 for Windows Server 2003 x64 Edition
• XenApp 5.0 for Windows Server 2003 x64
• XenApp 5.0 for Windows Server 2003 x86

Description :

• Using tool to create Service ID ctx_cpsvcuser in Citrix XenApp servers.

How To Do :

1. Download the re-creation tool here.
2. Upload the files to Citrix server.
3. Run command prompt, browse to the uploaded folder, and run below command.

   

   32-bit : CtxCpsvc10.exe –install | 64-bit : CtxCpsvc10_x64.exe –install

   
   
4. once done, double check the Citrix Print Management service. Ensure it can be started and set to Automatic.

Reference :

• http://support.citrix.com/article/CTX113554/

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No Printers Listed in Citrix XenApp Session - Citrix Print Management Service Not Listed

Printing is one of our important tasks in office. Those documents could be cinema online tickets, flights boarding pass, La Liga timetable... oh, all of those are not office-related. Nevertheless, we still need to print officer documents.. erm, resume for interviews, perhaps? =D

This post is to discuss of one possible issue, Citrix Print Management and Printer Spooler Services. Other possible issues will be discussed in other posts. I don't want to make this posts too lengthy (come on, just admit you are too lazy, Heiry...)



Issues :

• Users may received one or more errors regards to printing. Below are some of the error examples :
  
  

 - or - 

• Meanwhile from server perspective, no printers listed in Printer and Faxes

Troubleshooting 

1. Right click at My Computer, and click at Manage
   
   
   
   
   
2. From Computer Management Console, go to Services. Check whether those services are Started / Not Started / Not listed in Services. In below screenshot, Citrix Print Management service is not registered.

Resolution :

• If those Services are not started, re-start them.
• if Citrix Print Management Service is not listed, re-register the service by following below steps. 

1. Run CMD, and browse to %ProgramFiles%\Citrix\System32
   
2. Run below command
   
   cpsvc.exe -install

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