Mechanical APDL Basic Analysis Guide - Ansys

Chapter 21: Memory Management and Configuration
By changing the amount of ANSYS work space, you are in effect changing the available scratch space. This
is because the database space is held constant at 512 MB for 64-bit machines or 256 MB for 32-bit machines
(as illustrated in the following figure).
Figure 21.3 Changing ANSYS Work Space
Total =
512 MB
(default)
Total =
400 MB
256 MB 256 MB
Database Space Scratch Space
256 MB 144 MB
Database Space
Scratch Space
Only scratch space is changed, and database space is held constant.
The following list describes situations in which you may need to change ANSYS work space:
• Boolean operations among several volumes (for example, VADD,ALL). You need more scratch space in
such a case. This is an example where a large memory space may be needed temporarily and may be
satisfied from system virtual memory.
• Several users sharing one ANSYS installation (such as in a training class). Because all users share the
available memory (real memory plus system virtual memory), having less ANSYS work space requested
by each user would allow more users to run simultaneously (with correspondingly smaller model sizes
available for each user).
• Some analyses and analysis options require more work space, including random vibration (PSD) analysis,
etc. In the case that such an analysis is right at the limit of physical memory, you should conserve
memory by reducing database memory. In cases where you are running up to the physical limits of the
machine, increase the initial memory block given to ANSYS in order to maximize the possibility of
memory reuse within the ANSYS runs.
• Large number of element or nodes. The larger the number of active elements or nodes in your model,
the more scratch space needed.
Most solvers in ANSYS now use approximately 1 GB of memory per million degrees of freedom (DOFs). If
models are dominated by 2-D or shell elements, the memory requirement will be lower; if they are dominated
by 3-D higher-order brick elements, the memory requirement will be higher. The sparse solver will run larger
jobs in out-of-core mode and will require disk space of approximately 10 GB per million DOFs. The disk
memory requirement varies in the same increasing manner for shell 2-D models versus solid 3-D models. If
the solver memory estimate far exceeds the default memory for ANSYS, try increasing the initial memory
allocation for ANSYS.
21.3.3. Changing Database Space From the Default
This is done by requesting more or less database space. Given a fixed amount of ANSYS work space, allocating
more database space leaves less for scratch space and vice versa, as illustrated in the following figure.
310
Release 13.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.