If a source file is large, especially if it is an XML file, it makes sense to split it into multiple smaller files, and then process them one-by-one in a loop.
while splitting the files, Etlworks Integrator consumes only a minimum amount of RAM and CPU cycles, which allows it to work with very large files without blocking other tasks.
Read about splitting files.
Read about performance tips when working with files.
Also, read about merging files.