As a result of a limitation of the OS/400 operating system, it is not possible to create an individual storage object with more than 16 MB. Additional key words
This results in restrictions with regard to the maximum size of some R/3 buffers.
PXA, table buffers, ATP, PAGING, iSeries Cause and prerequisites
16 MB limit in OS/400 for individual storage objects. Solution
https://service.sap.com/sap/support/notes/121625 (SAP Service marketplace login required)