What is LHC?

The IMA service running on each Presentation Server downloads the information it needs from the central data store into a local MDB database called the local host cache, or “LHC.” (The location of the local host cache is specified via a DSN referenced in the registry of the Presentation Server, at HKLM\SOFTWARE\Citrix\IMA\LHCDatasource\DataSourceName. By default this is a file called “Imalhc.dsn” and is stored in the same place as MF20.dsn.) Each Presentation Server is smart enough to only download information from the data store that is relevant to it, meaning that the local host cache is unique for every server. Citrix created the local host cache for two reasons: 1. Permits a server to function in the absence of datastore connectivity. 2. Improves performance by caching information used by ICA Clients for enumeration and application resolution. The LHC is an Access database (Imalhc.mdb) stored default in the path "\Citrix\Independent Management Architecture" folder. LHC contained the following information: 1. All servers in the farm, and their basic information. 2. All applications published within the farm and their properties. 3. All Windows network domain trust relationships within the farm. 4. All information specific to itself. (product code, SNMP settings, licensing information) The LHC is critical in a CPS environment. In fact, it's the exclusive interface of the data store to the local server. The local server's IMA service only interacts with the LHC. It never contacts the central data store except when it's updating the LHC. If the server loses its connection to the central data store, there's no limit to how long it will continue to function. (In MetaFrame XP, this is limited to 48 or 96 hours, but that was because the data store also store license information.) But today, the server can run forever from the LHC and won't even skip a beat if the central connection is lost. In fact now you can even reboot the server when the central data store is down, and the IMA service will start from the LHC with out any problem. (Older versions of MetaFrame required a registry modification to start the IMA service from the LHC.) The LHC file is always in use when IMA is running, so it's not possible to delete it or anything. In theory it's possible that this file could become corrupted, and if this happens I guess all sorts of weird things could happen to your server. If you think this is the case in your environment, you can stop the IMA service and run the command "dsmaint recreatelhc" to recreate the local host cache file, although honestly I don't think this fixes anything very often. Local Host Cache is synchronised with the Data Store by the Zone Data Collector for every 30 minutes and it can also be configured through registry

www.myxenapp.com

www.myxenapp.com

TS CAL

A good example to what to use is if you have a call centre with 25 client machines. To start with you work 9 to 5 with all 25 connected. With citrix as well you would need 25 PS licenses, and 25 TS cals of either Device or User. Making sure that the citrix servers are set to the right TS cal version. If you change to 24x7 with 3 shifts working 8 hours then you would only ever have 25 citrix connections con current, so you would need 25 licenses, but TS is different. If you use per user license then you would need 75 licenses as you have potentially 75 users that are connecting. If you have TS cals per device then you would still only need 25 licenses as you only have 25 devices that are connecting to your servers. If you then have other servers that these users need to connect to that are TS servers then they don't need additional licenses if the license mode eg user/device are the same as they already have a license.

per device - if you own 25 citrix license you will need 25 ts cals,
that would be a 1 to 1 ratio.

Per user - you would need 25 CPS X amount of user.

http://www.xenwiz.blogspot.com/

http://www.xenwiz.blogspot.com/

http://knowcitrix.hpage.co.in/data_collector_51689109.html#.UNP_T-SOSdI