Creating custom objects in Clarity PPM is very slow, particularly when it is created as a subobject to the project object.
Release: Any
"The product supports up to 500 total attributes for each object. However, we recommend that you do not assign more than 100 attributes to a single custom object. A high number of attributes can result in performance issues and the potential failure of subsequent upgrades. Consider creating a subobject rather than assigning many custom attributes to a single object."
This also can cause Performance issues when Creating or Updating Attributes