Symptoms
An ESXi/ESX host in vCenter Server reports the error:

Unable to apply DRS resource settings on host. The operation is not allowed in the current state. This can significantly reduce the effectiveness of DRS.
WARNING: UserDuct: 184: Cannot allocate a new data segment, out of memory
 Resolution
Note: The resolution in this article works only if your environment does not include NSX or VMware Horizon View or VSAN. To resolve this issue if your environment includes NSX/View/VSAN, contact VMware Support.

This warning does not have any impact on production and can be safely ignored.

To resolve this issue, restart the management agents (hostd and vpxa) on the host.

If the problem persists after restarting the management agents, remove the host from the cluster and then re-add it to the cluster:
  1. Place the host into maintenance mode.

    Note: If DRS does not migrate the virtual machines to other hosts, migrate them manually.
     
  2. Ensure that there are no virtual machines running on the host.
  3. Remove the ESXi/ESX host by dragging it out of the cluster.
  4. Re-add the ESXi/ESX host by dragging it into the cluster.
  5. Exit from maintenance mode.
 Related Information
"Unable to apply DRS resource settings on host" warning in summary tab of the ESXi host
Restarting the Management agents in ESXi
El host ESX/ESXi en vCenter Server informa el error: No se puede aplicar la configuración de recursos DRS en el host. La operación no está permitida en el estado actual
vCenter Server 中出现 “无法在主机上应用 DRS 资源设置 (Unable to apply DRS resource settings on host)” 错误
vCenter Server の「DRS リソース設定をホストに適用できません (Unable to apply DRS resource settings on host)」エラー
 Update History
07/12/2012 - Added ESXi 5.0 and vCenter Server 5.0 to Products
01/16/2013 - Added ESXi 5.1 and vCenter Server 5.1 to products
02/22/2013 - Added WARNING symptom
03/20/2013 - Removed vCenter version 4.1 in symptoms section as it is applicable for all versions
07/28/2015 - Added 6.0 products