By default, tiImport.exe takes advantage of RAM that is available to it. However, you may not want to use so much memory, in which case it is possible to buffer data to disk while a data extraction is being run by
including the keyword USEDISK.
IMPORT table=USEDISK a1.table1
This loads data in chunks of 1,000,000 rows, saving to a temp file. Data is then Columnized to a different file containing an InMemoryTable. The table is loaded in its entirety into memory only when finished.