A page file is a file used for paging. A page file can also be used for swapping processes out of memory if no Swap File is installed and the system parameter NOPGFLSWP is not set, and for writing a crash dump if the system dump file does not exist in SYS$SPECIFIC:[SYSEXE].
There are two types of page files, primary and secondary. The primary page file is PAGEFILE.SYS located in SYS$SYSTEM; the secondary page file can be anywhere on the system, including devices other than the system disk. The primary page file can be removed if necessary.
Page file size is limited by 128 Gb.