Per-VDOM resource settings
While Global resources apply to resources shared by the whole FortiGate unit, per-VDOM resources are specific to only one Virtual Domain.
By default all the per-VDOM resource settings are set to no limits. This means that any single VDOM can use up all the resources of the entire FortiGate unit if it needs to do so. This would starve the other VDOMs for resources to the point where they would be unable to function. For this reason, it is recommended that you set some maximums on resources that are most vital to your customers.