See Also
The following options are all contained on the Storage tab after choosing the Power Flow Solution page of the Simulator Options.
Simulator offers the ability to restore either the last power flow solution state or the state of the system immediately before the last solution attempt. If your system has insufficient memory and you are working with large systems, you may wish to disable one or both of these options.
Disable "Restore last solution"
Restoring the last solution will undo any changes made to the data that were made after the last successful solution and return the case to the last valid solution. For large cases, the amount of memory required to store the last solution can be significant. If this option is checked, Simulator will not store this information in memory, and the last solution cannot be restored if a solution fails.
Disable "Restore state before failed solution attempt"
Restoring the state before failed solution attempt will undo only the attempted solution, but will retain any changes to data that were made before the solution process. This allows the user to return to the point just before the solution in order to add or remove changes in an effort to obtain a valid solution. For large cases, the amount of memory required to store the state before a solution attempt can be significant. If checked, Simulator will not store the state information in memory, and the state before the failed solution cannot be restored.
Even if you are not disabling these options, these system states might not be available for restoration under a couple of situations: switching to Edit Mode or adding or deleting a MW Transaction between areas will destroy these system states. The system states will be created again once a power flow solution is attempted, but the system states from any previous solutions will be destroyed.