There is a difference between Load all and Expandable subfile while writing the records to Subfile.
Incase of <b>Load all</b> subfile, All the records will be read from PF and will write into Subfile.
Eg. If we have 100 Records in PF and we are displaying 10 Records in Subfile at a time.
All 100 records will get written to subfile at once.
Incase of <b>Expandable</b> Subfile, The records which we are displaying on the screen will get written into subfile.
If we consider above exapmle, For the first time We display Subfile only 10 records will get written, and if we use PAGEDOWN keyword, the next 10 records will get written into Subfile before display.