Onix creates temporary files during some of its processing such as during the indexing process or when so many search results are returned, that a virtual method of storing the search results is needed.
For this reason, you may set the location that these temporary files are created and stored. If you do not, these files will be created in whatever the default location is for your system and OS.
As one might expect, the API for this is quite simple. ixSetLocationForTemporaryFiles, sets the location for the temporary files and ixGetLocationForTemporaryFiles gets the location previously set (if any).
During the indexing process a number of temporary files are generated. In general, you will want to have disk space available several times the amount of data indexed during any given indexing session. You can keep track of the amount of data written to disk via a call to ixGetTempDiskSpaceUsage which reports the total size of all the temporary files generated. You will want to make sure you have at least twice the amount of space taken for the temporary files available to allow for space to process and compress these files.