Mechanical APDL Basic Analysis Guide - Ansys

Chapter 21: Memory Management and Configuration
space is where all internal calculations are done - element matrix formulation, equation solution, Boolean
calculations, and so on. The default total work space for 64-bit machines is 1 GB (1024 MB), of which 512
MB are assigned to database space, and 512 MB are assigned to scratch space. For 32-bit machines, the
default work space is 512 MB, of which 256 MB are assigned to database space, and 256 MB are assigned
to scratch space. (Part of the scratch space stores binary file buffers; see the description of NUM_BUFR later
in this chapter.)
Figure 21.2 ANSYS Work Space
If your model database is too big to fit in the database space, the ANSYS program will first try to allocate
additional memory to hold it (64-bit systems only). If it cannot, the program uses ANSYS virtual memory,
which is, again, a portion of the hard disk used for data overflow. The main difference between system virtual
memory and ANSYS virtual memory is that the former uses system functions to swap data between memory
and disk, whereas the latter uses ANSYS programming instructions. The file used for ANSYS virtual memory
is called the page file and has the name Jobname.PAGE. Its size depends entirely on the size of the database.
When the page file is first written, the program issues a message to that effect. Use of the page file is not
desirable because it is a less efficient way of processing data. You may be able to prevent it by allocating
more database space (discussed in How and When to Perform Memory Management (p. 308)).
If internal calculations can't fit in the scratch space, the ANSYS program will attempt to allocate additional
memory to meet these requirements. If this occurs, you will see an alert message informing you that the
problem has grown beyond the specified memory allocation and that ANSYS has allocated additional memory.
In general, you should have enough real physical memory to comfortably run an ANSYS job. If you are using
extra memory beyond physical memory only temporarily (such as for meshing or equation reordering), the
performance impact from using virtual memory will be small. However, in a situation such as the matrix
storage for the PCG solver exceeding physical memory, the performance can be as much as ten times slower
for the solve command.
21.3. How and When to Perform Memory Management
Normally, there is no need to concern yourself with memory-management issues in ANSYS. The ANSYS
memory manager can allocate extra memory from the system when it needs to in almost all cases.
The following sections provide guidance as to when it is likely that you will need to use the -m command
line option.
21.3.1. Allocating Memory to ANSYS Manually
21.3.2. Changing the Amount of ANSYS Work Space
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