Mechanical APDL Basic Analysis Guide - Ansys

21.3.3. Changing Database Space From the Default
21.3.1. Allocating Memory to ANSYS Manually
The -m command line option allows you to manually set the size of the initial block of memory used by
ANSYS. Memory allocated via the -m option exists in two contiguous blocks. For example, a -m setting of
1800 with a -db option of 300 instructs ANSYS to first allocate a 300 MB contiguous block of memory for
the database and then to allocate a 1500 MB contiguous block of scratch memory (1800 - 300 = 1500).
The current ANSYS default for all 64-bit systems is -m = 1024 and -db = 512. For 32-bit Windows and Linux
systems, the defaults are -m = 512 and -db = 256. Ideally, all ANSYS memory will be allocated from within
the initial block, allowing efficient reuse of memory blocks during various phases of simulation. When ANSYS
needs more memory, it will allocate from the system, automatically growing new blocks that are half the
size of the initial scratch memory block or the size of the new memory block allocation, whichever is larger.
Changing the default memory settings is only necessary when a job is failing due to insufficient memory
that may be caused by fragmented memory.
For example, if a large model requires a contiguous block of 800 MB for the sparse solver, the default memory
allocation will be insufficient (-m 1024 MB minus -db 512 MB = 512 MB contiguous memory). In this case,
ANSYS would try to allocate an additional 800 MB block of contiguous memory to satisfy the sparse solver
requirement, bringing the total memory requirement to 1800 MB (1024 default plus 800 additional). This
memory requirement may fail on smaller systems, especially 32-bit Windows systems. To accommodate this
model within the default memory availability, specify -db -100 (using a negative value will prevent the
program from allocating additional memory); this will result in an initial memory block of 924 MB, which is
sufficient to satisfy the sparse solver requirement of 800 MB. If you are running a 32-bit Windows system,
see Memory Usage on Windows 32-bit Systems for more information about that system.
21.3.2. Changing the Amount of ANSYS Work Space
The easiest way to do this is to use the work space entry option (-m) while activating the program, either
via the ANSYS launcher or via the ANSYS execution command. For example, to request 400 MB of ANSYS
work space (instead of the default of 1 GB for 64-bit machines or 512 MB for 32-bit machines), the ANSYS
execution command would read:
ansys130 -m 400
(The execution command syntax is system-dependent.)
When you use the -m option, system virtual memory is allocated at run time to achieve the work space requested.
Other ways to change the maximum ANSYS work space are:
• Specifying the work space size you want on the dialog boxes that appear when you select interactive
mode or batch mode from the ANSYS launcher.
• Using a different VIRTM_MB value in your config130.ans file. A later section in this chapter discusses
this file in detail.
Caution
21.3.2. Changing the Amount of ANSYS Work Space
Be careful when specifying a value for the -m option. Entering an amount larger than needed
will waste system resources and degrade system performance.
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