HP 3000 Manuals

Introduction to MPE XL for MPE V Programmers Migration Guide

Buffers and 
Disk Files 
(changed) 

In MPE XL, file system buffering is not performed for standard (file type 
option = STD) disk files in BUF mode.  Instead, records are transferred
directly between your local data area and the virtual space associated
with your file.  This means that, unlike MPE/V, using the blocking factor
to alter the buffer size will not have an impact upon the performance of
MPE XL applications.

Under MPE XL, data is transferred between the system and the data area
defined in your program in the same way it was transferred under MPE/V.
That is, for the standard disk files opened with the inhibit buffering 
options of HPFOPEN/FOPEN set to BUF (buffered mode), each read or write
operation transfers one logical record.  For standard disk files opened
with NOBUF (unbuffered mode), each read or write operation transfers one
physical record (block).

Because MPE XL does not implement system buffers for standard disk files,
the numbuffers option of HPFOPEN/FOPEN is meaningless for standard disk
files.

MPE/iX 5.0 Documentation