Open Ansys Help, select Mechanical APDL, Performance Guide, and look at section 4.2 on Understanding Memory… you can read the definintion of all the terms in the solution output file and see this illustration:
The solver can start off using in-core, and as the memory required increases as the solution progresses, the solver automatically switches to out-of-core. Then as the solution continues, at some point even more memory is required but there is no more. That is what the error message is telling you.
You are navigating away from the AIS Discovery experience