Mechanical APDL Basic Analysis Guide

Chapter 21: Memory Management and Configuration

The minimum amount of physical memory (RAM) recommended for the program varies from system
to system and is listed in your ANSYS, Inc. Installation Guide. In order to maximize performance on your
particular system, it is helpful to understand the memory-management scheme and some frequently
used terms concerning computer memory.

The following memory-management topics are available:

21.1. Work and Swap Space Requirements

21.2. How the Program Uses Work Space

21.3. How and When to Perform Memory Management

21.4. Using the Configuration File

21.5. Understanding Memory Error Messages

To learn how to improve analysis performance, see the Parallel Processing Guide and the Performance
Guide.

21.1. Work and Swap Space Requirements

The program itself requires some space to reside in memory, and it requires additional work space
memory. The work space defaults to 1 GB (1024 MB) for 64-bit machines, and 512 MB for 32-bit machines
(Linux and Windows). As shown in Figure 21.1: Comparing Available Memory (p. 327), the total memory
required for the program can exceed the amount of physical memory available. The additional memory
comes from system virtual memory, which is simply a portion of the computer's hard disk used by the
system to supplement physical memory. The disk space used for system virtual memory is called swap
space, and the file is called the swap file. On some systems it is referred to as a page file (not to be
confused with the page file). Other systems maintain multiple files, or even dedicat ed disk sectors to
act as virtual memory. The amount of swap space required for the program depends mainly on the
amount of physical memory available and the amount of work space allocated.

Due to the significant overhead incurred when writing data from memory to disk (or reading data from
disk to memory), it is generally recommended that virtual memory usage be avoided as much as possible.
A notable exception would be when trying to push a large simulation through solution on a machine
without enough physical memory to hold all of the data. In this case, however, minimal use of virtual
memory is still recommended; otherwise, the performance will be severely degraded.

Figure 21.1: Comparing Available Memory

ANSYS

Computer

ANSYS

Executable

ANSYS

Work Space

Physical

Memory

System Virtual Memory

(Swap Space)

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