Communicator e3000 MPE/iX Release 6.5 (Non-Platform Software Release C.65.00 (30216-90291)

Chapter 3 35
Growth Solution
MPE/iX Large Files Overview
of an ordinary fixed-length record file can affect the maximum size of file.
About this Document
This document is intended to describe all the external functions, features, and changes
that have been introduced with Large File support. The document itself is broken into four
sections:
• Large File Compatibility Issues. This section covers the small number of issues that
could arise when accessing Large Files.
• Changes to the Command Interpreter. This section describes the enhancements
that have been added to several CI commands to support Large Files and KSAM64 files.
• New and Enhanced Intrinsics. This section reveals the upgrades to several existing
intrinsics for Large File support, as well as introducing a new set of intrinsics to aid in
user-mapped file access.
• Miscellaneous. This section discusses the impacts of Large Files on various
subsystems and utilities, and covers other miscellaneous Large File topics.
Summary of Large File Compatibility Issues
This section covers the compatibility issues that users need to be aware of when dealing
with Large Files. In most cases applications and users are unaware that the file that they
are operating on is a Large File.
Even though Large Files are highly transparent, there are some rare situations that can
produce results that are either incompatible or in error when dealing with Large Files
instead of normally-sized files. The following sections highlight and describe the issues
that can affect access to Large Files.
User-mapped Access to Files
MPE/iX currently supports two types of user-mapped access to files; short-mapped access
and long-mapped access. Short-mapped access provides a 32-bit pointer for a user
application to directly access a file. There are several limitations to short-mapped access.
For example, a file must be 4MB or less and the total of all short-mapped access files for a
process must be less than 6MB. Long-mapped access provides a 64-bit pointer to access a
file of any size, up to the previous maximum file size of 4GB.
Record Size Maximum # of Records Maximum Object Size Maximum Resulting File Size
1 byte 2,147,483,647 128GB 2GB
40 bytes 2,147,483,647 128GB 80GB
60 bytes 2,147,483,647 128GB 120GB
80bytes 1,717,986,918 128GB 128GB