ERROR 101:
Memory allocation error.
Error 101 : There is not enough physical memory in the computer to analyze the study area.
1. Description
ERROR 101 occurs when the EPA SWMM engine underlying GeoSWMM cannot obtain enough computer memory to load, initialize, or run the model. This is not a hydraulic or hydrologic input error. It means the current model and analysis settings require more memory than the computer can provide, so SWMM engine stops before producing a complete set of results.
2. Technical Background
EPA SWMM allocates RAM up front to initialize the drainage network and supporting data structures, then allocates more as hydraulic and hydrologic calculations progress and results are stored.
ERROR 101 is generated when Windows cannot provide the system memory requested by the SWMM engine. This may happen when the model requires more memory than is available, or when available memory is fragmented or otherwise unavailable. Because the requested memory cannot be allocated, EPA SWMM terminates the simulation before producing results.
3. Resolution
Use the following steps in order: first determine whether memory demand comes from the model configuration, then reduce unnecessary model or output detail, and finally confirm whether the computer has enough resources for the revised simulation.
Caution: Before making diagnostic changes, save a separate copy of the model and perform troubleshooting on that copy. This preserves the original engineering model and makes it easier to compare results after temporary simplifications are restored.
Table 1 : Troubleshooting steps
Step | Action | Why It Helps |
|---|---|---|
1 | Confirm when the error occurs
| Identifies whether the memory demand is related to the model configuration or the computer environment. |
2 | Review model data and output settings
| Reduces the number of model objects and calculation arrays that EPA SWMM must keep in memory |
3 | Identify high-demand modules
| Helps identify which model components are increasing memory demand. |
4 | Free available memory
| Makes additional system memory available for EPA SWMM. |
5 | Check computer resources
| Increases the amount of memory available for large simulations. Virtual memory can support Windows operation, but it does not replace adequate physical RAM. |
6 | Verify the revised model
| Confirms that the model runs successfully and that the solution does not compromise the analysis objective. |
✓ Diagnostic Tip
If ERROR 101 occurs only for a specific project while smaller models run successfully, the issue is likely related to the memory demand of that project rather than the GeoSWMM installation. Running a shorter test simulation can help determine whether the model exceeds the available system resources. For exceptionally large models, consider upgrading the computer with additional RAM or running the model on a higher-specification computer with greater available memory and system resources.