The process of creating machines in XenDesktop via MCS can be split into 2 sections.

• Provisioning Scheme
• Machine creation.

Let us understand provisioning scheme step by step here:

1. What is Provisioning Scheme?

   1. Provisioning Scheme can be seen as a “template‟ used to store the parameters and create the VMs. It includes details like the CPU Count of the Master Image VM, the Memory Size of the Master Image VM as well as the location of the Master Image VM used in this provisioning scheme. All the parameters stored in a provisioning scheme can be obtained using the SDK

2. How a Provisioning Scheme is created?

   1. The first step to creating a new Provisioning Scheme is to create a workflow instance.
   2. Then we obtain and validate the details needed to create the Provisioning Scheme. Identity Pool is obtained by the AD Identity Service where the name of the Identity Pool will be the name of the catalog given by the Administrator on catalog creation. The name of the catalog will be placed in the metadata of this Provisioning scheme which is referenced by its unique workflow ID.
   3. Then the Provisioning Scheme is named using the Catalog Name and the Hosting Unit Name.
   4. When  all the machine information is stored in the Provisioning scheme workflow then Master Disk of the Virtual Machine is created.
   5. Once the newly consolidated Master virtual machine is replicated amongst all the different storage locations, the Provisioning scheme has been created and is ready to be used for virtual machine creation.

3. Association with MCS:

   1.  The creation of Machine happens the MCS creates a VM using the Metadata stored in the Provisioning Scheme. Here it will use a name based on the AD Identity that is to be used for that machine. At this point the VM has no disk attached.

If you need to change resources for existing machine catalog, you can check it here:

https://www.knowcitrix.com/posts/change-machine-catalog-resources/