RAM is a limited resource, while for practical purposes virtual memory is endless. With this structure, Microsoft uses a compilation file like that extra RAM, but in a transparent and flexible way, so that this file can be sized from 2 GB to any value we want to have.
What is a merge file and what is used for
Where the amount of memory used by all PC processes exceed the amount of RAM available, the wrap file goes into effect. This is a hard disk partition that acts as a virtual RAM, that is, used by Windows to "store" processes that are loaded into memory and that exceeds the maximum amount of RAM the system has.
Physically, this pairing file is called filefile.sys and is automatically placed on all storage units we have on a PC, though Windows allows us to set limits manually if we want to "not" consume all of the hard disk volume.
So the pairing file is the second RAM that Windows allocates space to storage to use only, so that when we have too many processes embedded in memory
How big should it be? Need to have it on PC?
According to Microsoft, The recommended page file size should be 1.5 times the maximum RAM size. In other words, if you have 4 GB of virtual RAM, this file should be 6 GB, and if you have 8 GB of RAM on your computer, the wrap file should be 12 GB in size.