Random machine catalogs
Maintain users' desktops by applying global updates, such as Windows updates, anti-virus software updates, or configuration changes, to the Master Image. Then modify the machine catalog to use the updated master image so users receive the updated desktop at their next logon. Using this method lets you make significant changes to users' desktops, including upgrading to a new operating system, for large numbers of users in one operation.
Static and Remote PC Access machine catalogs
You must manage updates to users' desktops outside of XenDesktop, either on an individual basis or collectively using third-party software distribution tools. For machines created through Provisioning Services, updates to users' desktops are propagated through the vDisk.
Citrix recommends that you save copies or snapshots of master images before you make any updates. The Database retains a historical record of the master images used with each machine catalog. To quickly revert a machine catalog to use the previous version, preserving the old Master Images in their original state, that is, do not delete, move, or rename the master images. You can then use the previous version of the Master Image should users encounter problems with updates that you have deployed to their desktops, thereby minimizing user downtime.