Checking the amount of free memory is helpful to determine if a given ANSYS solution will solve in-core or out-of-core.

The top command is very helpful in reviewing running processes, but it includes cached files in the “used” memory summary:

top - 20:59:59 up 7 days,  7:27,  1 user,  load average: 0.00, 0.00, 0.00
Tasks: 146 total,   1 running, 145 sleeping,   0 stopped,   0 zombie
Cpu(s):  2.0%us,  1.0%sy,  0.0%ni, 97.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   2009564k total,  1568788k used,   440776k free,       76k buffers
Swap:  1951888k total,    30680k used,  1921208k free,  1206676k cached

Output from free -m is shown below:

             total       used       free     shared    buffers     cached
Mem:          1962       1531        430          0          0       1178
-/+ buffers/cache:        353       1609
Swap:         1906         29       1876

Notice in the above output that 353 MB is really used, not 1.5 GB as reported by top.

One would not need to manually clear the cache, although it is possible to do so. The sync command ensures that all current data in memory is written to disk, so this should be done first. As superuser, issuing echo 3 > /proc/sys/vm/drop_caches will free pagecache, dentries, and inodes. (Echoing 1 will just free pagecache while 2 will just free dentries and inodes.)