Just in Time (JIT) deployment is a centralized, automated update facility for deploying Packages set up to use Just in Time processing.
All the Packages associated with an Application are installed on a centralized Application Server, that is, the initial Version and any subsequent upgrade Versions or Patches.
Just in Time installation needs to be set up when the initial Application Version is installed. This initial Version needs to be applied to the target PCs using the MSI.
After the initial installation, each time a user launches the Application from a Target PC, the Target PC connects to the Application Server to see if new upgrades are available to install. Any new upgrades will be automatically installed before the Application is launched.
This option can greatly reduce the administration costs associated with deploying application upgrades.
Refer to Just In Time Upgrade Guidelines for more information.