# VM Hot Add CPU Or Memory

<code class="expression">space.vars.product\_name</code> supports hot-add of CPU and / or memory resources to a running virtual machine. Using this feature, you can increase CPU cores or memory allocated to a running VM, without having to power-cycle it. This is valuable for production VMs that need more resources to meet workload demands but that can not be powered off.

### Pre-requisites <a href="#pre-requisites" id="pre-requisites"></a>

* Read more here about [Zero-Size Flavor](https://docs.platform9.com/private-cloud-director/virtualized-clusters/flavorless-vms-with-hot-plug#zero-size-flavor). Using **zero-size flavor** when creating your VM is a requirement for hot-add. Before you can hot-add CPU or memory resources to a VM, the VM must have been created using zero-size flavor.

### Hot-add CPU or Memory to a Running VM <a href="#hot-add-cpu-or-memory-to-a-running-vm" id="hot-add-cpu-or-memory-to-a-running-vm"></a>

1. Select a powered-on VM that was created with a zero-size flavor.
2. On the VM grid view, navigate to **▷** **Other** **Actions ▷ Hotplug**.
3. Enter the new vCPU and/or memory value for the VM. The maximum allowable values are automatically set based on the VM configuration.
4. Click Hotplug VM.

### Limitations <a href="#limitations" id="limitations"></a>

* Hot add can only be used to increase the current CPU or memory allocation of a running VM. Reducing currently allocated CPU or memory is supported only while the VM is stopped.
* You can not use the hot-add feature to resize the disk of a running VM today.