The below post is related to an archived discussion
In absence of a posted answer to the question of changing the location of the out-of-core files due to memory limitations, here is a proposed solution:
When MUMPS switches to out-of-core mode due to in-core memory limitations, data will be written on the disk in the default temporary folder defined in the Comsol preferences, until the disk space becomes saturated and Comsol throws an out-of-core memory error.
If you want to specify a different location (e.g to a larger drive other than the default installation drive), you can launch Comsol from the terminal with the command:
$>comsol -tmpdir pathtofolder/
(Or from the software GUI interface, Options>Preferences>Files => modify path for "Folder for temporary files")
Beside being used for mesh data, this folder is where multiple out-of-core MUMPS files will be created while in out-of-core mode.