This chapter explains memory usage in Mechanical APDL and gives recommendations on how to manage memory in order to maximize performance. Since solver memory usually drives the memory requirement for a simulation, the details of solver memory usage are discussed here. Solver memory for direct and iterative solvers, as well as shared-memory and distributed-memory solver implementations, are described and summarized in Table 4.1: Direct Sparse Solver Memory and Disk Estimates and Table 4.2: Iterative PCG Solver Memory and Disk Estimates. Information on commonly used eigensolvers is also provided in this chapter.