Enumerated type listing flags that can toggle on or off certain calculations related to MEP systems. 
   Namespace:   Autodesk.Revit.DB.Mechanical  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 21.0.0.0 (21.1.1.109) 
  Since:  2012 
Syntax
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Members
| Member name | Description | 
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| All | System calculation is on for everything (with every bit being 1) | 
| None | System calculation is off | 
| Flow | System calculation is only for flow | 
| Volume | This mode is obsoleted in Revit 2017. | 
| Performance | This mode is reserved for limiting the system propagation and other performance-boosting options. Note that the system-related functionalities might be traded off for faster layout capability in large system when this mode is on. Be careful that this mode is NOT included in the "All" mode. |