OS/2 Professional/OS2PRO194.ISO/os2/info/faq/os2_21/21perf.inf

OS/2 Help File | 1993-07-12 | 26.3 KB | 660 lines

ΓòÉΓòÉΓòÉ 1. Version Notice ΓòÉΓòÉΓòÉ

Information

Copyright International Business Machines Corporation 1993. All rights
reserved.
Note to U.S. Government Users Documentation related to restricted rights Use,
duplication or disclosure is subject to restrictions set forth in GSA ADP
Schedule Contract with IBM Corp.


ΓòÉΓòÉΓòÉ 2. Trademarks referenced ΓòÉΓòÉΓòÉ

The following products are referenced in the document:

o OS/2, Personal Systems/2, PS/2 and Micro Channel are registered trademarks of
  the International Business Machines Corporation
o Presentation Manager and WIN-OS/2 are trademarks of the International
  Business Machines Corporation
o Intel is a registered trademark of the Intel Corporation
o Microsoft and Microsoft Windows are registered trademarks of Microsoft
  Corporation

This paper is designed to provide information on improvments in the OS/2 2.1
release. It contains details of the performance improvements incorporated since
OS/2 2.0.

System Requirements Section 1 covers system requirements.

The Graphics Subsystem Section 2 contains information on the changes made in
the graphics sub-system.

Video Display DriversSection 3 contains information on video display drivers,
including new support.

WIN-OS/2 Section 4 explains the enhancements made in WIN-OS/2, including
seamless support, clipboard and DDE, and the new settings available.

General Performance OptimizationsSection 5 covers general system performance
optimizations.

Memory reduction items are covered in Memory ReductionSection 6

VDMSection 7 covers VDM support and customization of the AUTOEXEC.BAT.

OtherSection 8 covers the other areas of performance improvements, including
printing and communication support.

Installation changes are covered in InstallationSection 9


ΓòÉΓòÉΓòÉ 3. Introduction ΓòÉΓòÉΓòÉ

OS/2 version 2.1 continues the OS/2 product line. The main objective for this
release were to provide Windows 3.1 application support, to incorporate all
service fixes, to continue migrating OS/2 components to 32-bit, to increase
function and to provide additional display driver support. The fol lowing
information applies to the final release of OS/2 2.1. The information covered
pertains to performance improvements made for this release, and functional
changes that affect performance. This document covers many of the changes, but
not all the changes and improvements that went into OS/2 2.1. Other
documentation is available that contains information on all aspects of this
release, and this document should not be viewed as containing all changes made
since release 2.0.


ΓòÉΓòÉΓòÉ 4. System Requirements ΓòÉΓòÉΓòÉ

The system requirements have changed little from OS/2 2.0. The memory
requirement for OS/2 2.1 is similar to the memory requirement for OS/2 2.0. The
DASD requirement has increased about 7MB, depending on the installation options
selected.


ΓòÉΓòÉΓòÉ 4.1. Hardware Configurations for OS/2 ΓòÉΓòÉΓòÉ

2.1

OS/2 2.0 is designed for personal computers with the following minimum
requirements:

o Intel (or compatible) 80386SX microprocessor
o 4MB of memory
o 60MB hard disk with 20-40 MB of free disk space
o 2-button mouse or other pointing device

It is recommended that systems should have a minimum of 6 megabytes of memory
for good performance.


ΓòÉΓòÉΓòÉ 4.2. WIN-OS/2 DASD Requirements ΓòÉΓòÉΓòÉ

In OS/2 version 2.1, Windows support can be installed on a partition different
from the partition where OS/2 is installed. This will allow moving some of the
disk space requirement to another partition. While the same amount of disk
space is required in total, this feature allows flexibility when available
space on the install partition is limited. The total is approximately 8MB of
DASD. See the installation guide for more information.


ΓòÉΓòÉΓòÉ 5. The Graphics Subsystem ΓòÉΓòÉΓòÉ

In OS/2 2.1, the graphics engine was rewritten from assembler using the 32-bit
IBM C Set/2 compiler. In addition to being a fully 32-bit engine, many graphics
operations were enhanced for better performance. The 32-bit engine uses more
memory than the 16-bit version, so effort was made to optimize the memory usage
of the 32-bit graphics engine for both the Workplace Shell and graphical
applications. Frequently used functions and routines in the graphics engine
were tuned and linked together to minimize the system working set. This process
is referred to as page tuning. The performance items for the OS/2 graphics
subsystem are listed as follows:

o Conversion to 32-bit

  The conversion of the engine to 32-bit has the following advantages:,

   - The flat memory model, eliminating segmentation overhead.
   - Allows optimization of 32-bit presentation drivers.
   - Eliminates the conversion (thunk) overhead between the graphics engine and
     the 32-bit components in the system.
   - Eliminates thunking in graphics calls from 32-bit applications.

o Palette Manager Support so applications can share access to the hardware
  color table.

o New APIs (GPIPolygons) were added for faster and easier application
  development.

o Page tuning to reduce memory requirements


ΓòÉΓòÉΓòÉ 6. Video Display Drivers ΓòÉΓòÉΓòÉ

Both presentation manager display drivers, and WIN-OS/2 display drivers have
been changed to provide additional function and improve performance.


ΓòÉΓòÉΓòÉ 6.1. Presentation Manager Display Drivers ΓòÉΓòÉΓòÉ

The Presentation Manager display drivers have several performance enhancements.
By display driver, they are listed here:

o VGA driver

  The new VGA driver is 32-bit. It has the advantages of 32-bit code, but, from
  the viewpoint of performance, it has some improvement over the 16-bit
  version.

o XGA driver

  The XGA driver was also converted to 32-bit. It has visible performance
  improvement over its 16-bit counterpart. The XGA driver also makes use of the
  new hardware features of the latest XGA-2 display adapter. It provides
  non-interlace support, takes advantage of the external polling capability,
  and can display up to 64K colors in low resolution modes (640 x 480, 640 x
  400).

o SVGA driver

  There was no SVGA support supplied in OS/2 2.0. In OS/2 2.1, several SVGA
  chip sets are supported. The drivers are 32-bit. Performance comparisons
  between OS/2 2.1 and OS/2 2.0 with generic 16-bit drivers (available from
  venders) shows that OS/2 2.1 with SVGA is visibly faster. OS/2 2.1 supports
  the following SVGA chip sets:

   - ATI Technologies Inc., VGA Wonder XL (Rev. 2.0 or higher).
   - Headland Technology Inc., Video Seven, Chip Type: HT209.
   - Trident Microsystems, VGA Card, Chip Type: TVGA 8900B and TVGA 8900C.
   - Tseng Laboratories, Chip Type: ET4000.
   - Western Digital Corporation, Paradise, Chip Type: WD90C00, WD90C11,
     WD90C30, and WD90C31.
   - Cirrus Logic Inc., Chip Type: CL-GD542X, family 5422 & 5424.
   - IBM Corp., Chip Type: IBM VGA 256c

  The default driver during installation is VGA driver (640 x 480 x 16 colors).
  The resolution may be changed by installing the drivers for the desired
  resolution.

  At least 0.5 MB VRAM is needed to install the SVGA drivers. At 0.5 MB VRAM,
  only the OS/2 SVGA resolution of 640 x 480 x 256 colors is supported. Both
  the 1024 x 768 x 256 colors and 800 X 600 X 256 colors resolutions require 1
  MB VRAM.

o 8514 driver

  The 8514 PM display driver support has been converted to 32-bit. Its
  performance is better than the 16-bit version.


ΓòÉΓòÉΓòÉ 6.2. WIN-OS/2 Display Drivers ΓòÉΓòÉΓòÉ

o Seamless Support (WIN-OS/2)

  WIN-OS/2 display drivers have been improved for both performance and
  functionality. WIN-OS/2 display drivers are automatically copied at install
  time (if WIN-OS/2 is installed) for the display type selected at
  installation. WIN-OS/2 is available in full screen or seamless (windowed)
  sessions. Seamless support is provided in the display device driver, and that
  support has expanded. In version 2.0, only the VGA display driver provided
  seamless support. All other display drivers supported WIN-OS/2 in full screen
  only. In version 2.1, VGA, XGA, SVGA and 8514 display drivers shipped with
  OS/2 support seamless execution for WIN-OS/2.

o Code Path Reduction p. Code paths have been reduced to improve the overall
  performance of the WIN-OS/2 display drivers, in both full screen and seamless
  modes.


ΓòÉΓòÉΓòÉ 7. WIN-OS/2 ΓòÉΓòÉΓòÉ

A significant enhancement provided in OS/2 2.1 is the support for Windows 3.1
applications. Performance of WIN-OS/2 has also been substantially improved. A
new mode called Enhanced Compatibility Mode enables a number of Windows 3.1
enhanced mode applications to run.

The Clipboard and DDE support has been redesigned, including virtual rendering
of clipboard data. Several enhancements were made to display drivers.


ΓòÉΓòÉΓòÉ 7.1. Enhanced Mode Compatibility ΓòÉΓòÉΓòÉ

In OS/2 2.0, support was provided in WIN-OS/2 3.0 to enable Windows 3.0
applications to run in standard and real modes. In OS/2 2.1, the support has
been upgraded to support standard and enhanced modes for Windows applications.

The Enhanced Mode Compatibility enables running a number of Windows 3.1
enhanced mode applications under OS/2 2.1. It is important to realize that this
is not an implementation of Windows 3.1 enhanced mode, but a mode specific to
WIN-OS/2 3.1. This illustrates the flexibility of OS/2 and its power in
blending different application environments into an integrated platform. The
major benefit to Windows 3.1 users of enhanced mode was virtual memory, which
OS/2 users had since OS/2 2.0. Like the previous WIN-OS/2, a special VDD is
provided to emulate a DPMI server. The WIN-OS/2 3.1 kernel is loaded into the
VDD to directly service the requests of Windows applications running in that
VDM. To preserve the integrity of the system and avoid having duplicate virtual
device drivers (one running on top of the other), the WIN-OS/2 Enhanced Mode
Compatibility does not use the Windows enhanced mode virtual device drivers
(VxDs). As a result, Windows 3.1 applications which access VxDs will not run in
the WIN-OS/2 3.1 Enhanced Compatibility Mode. Windows applications requiring
real mode to execute, will only be supported in the 2.0 version of WIN-OS/2.

An application can be set up to run in the Enhanced Compatibility Mode by
setting the WIN_RUNMODE to "3.1 Enhanced Compatibility Mode". This setting can
be found in the Settings notebook for the application object.

Enhanced Compatibility mode sessions can be started from an OS/2 or DOS command
line by typing WINOS2 /E or WINOS2 /3. To start an application to run in the
Enhanced Compatibility mode, (for example hello.exe), you would type WINOS2 /3
hello.exe.

The enhancements made to WIN-OS/2 are as follows:

OS2K386.EXE

This new WIN-OS/2 3.1 (OS2K386.EXE) kernel replaces the OS2/2 2.0
(OS2K286.EXE). It has all the functionality of the Windows 3.1 kernel
(KRNL386.EXE). This kernel provides memory, program loading and scheduling for
WIN-OS/2 3.1. It uses the DPMI interface for memory and interrupt management.
It executes in full screen and seamless modes, using the current VDM
architecture with DOS emulation.

OS2USER.EXE

This kernel is similar to the Windows 3.1 USER.EXE with all the seamless
support code ported from the WIN-OS/2 3.0 USER.EXE. The kernel contains the
user interface and windowing parts of Windows 3.1.

OS2GDI.EXE

This kernel is similar to Windows 3.1 GDI.EXE. The kernel contains the graphics
device interface with the palette management code ported from WIN-OS/2 3.0. The
print spooler mapping that eliminates double spooling by Windows applications
has also been ported from WIN-OS/2 3.0.

SESMGR.DLL

Two new program types have been added to the session manager to support Windows
3.1 standard mode:

o PROG_31_STDSEAMLESSVDM - Windows 3.1 program which will execute in its own
  windowed and WIN-OS/2 session.
o PROG_31_STDSEAMLESSCOMMON - Windows 3.1 program which will execute in a
  common windowed and WIN-OS/2 session.

OS2KRNL

A new return value to DosQAppType is used to determine the Windows version (3.0
or 3.1) of the application. This value is used in the migration of Windows
applications to the appropriate common VDM.

Workplace Shell

The Session page of WIN-OS/2 objects has been changed to enable the shell to
detect if WIN-OS/2 3.1 is installed and display the updated session.


ΓòÉΓòÉΓòÉ 7.2. Other WIN-OS/2 Improvements ΓòÉΓòÉΓòÉ

WIN-OS/2 Setup Icon

Settings for WIN-OS/2 sessions can be changed globally, using the WIN-OS/2
Setup icon found in the System Setup folder. Settings can also be changed for
specific sessions, using the application settings notebook. Changes to the
WIN-OS/2 Setup icon will change all Windows applications that start after the
change is made. The WIN-OS/2 Setup settings will not override  any custom
values set for applications. This allows changing settings easier for multiple
Windows applications.

CLIPBOARD and DDE

Both Clipboard and DDE have undergone major redesign since OS/2 2.0. Most
noticeable is the user interface and the method in which data is exchanged
between VDM's. Under WIN-OS/2 3.1, clipboard and DDE agents are no longer
executables. They have been implemented as DLLs that are loaded by their
respective "Shields". The windows shield (winsheld.exe) loads "winsdde.dll" and
"winsclip.dll", while the PM shield (pmviop.dll) loads "pmdde.dll" and
"pmclip.dll". The settings for making clipboard and DDE globally public (that
is, DDE is exported outside of the PM session) are now to be found in the
"WIN-OS2 Setup" object. This object is typically found in the "System Setup"
object, which in turn is found in the "OS/2 System" folder.

Virtual rendering of clipboard data was added in this redesigned clipboard.
This means that data conversions only take place if the client requests the
clipbaord data in a different data format) In OS/2 2.1 data placed in the
clipboard (cut or copied) was converted in all supported formats 'just in case'
it was asked for in a different format. While this improved the paste time,
that time and memory used at cut/copy time overshadowed the savings to paste.
The new design requires less memory, resulting in the ability to cut/copy
larger items.

In general, changes that were made to the clipboard and DDE include:

o PMCLIP.DLL replaces CLIPOS2.EXE (CLIPOS2.EXE is now just a viewer).
o PMDDE.DLL replaces PMDDE.EXE.
o WINSCLIP.DLL replaces CLIPWOS2.EXE (CLIPWOS2.EXE is now obsolete).
o WINSDDE.DLL replaces DDEAGENT.EXE.
o VWIN.SYS replaces VDMSERVER.EXE.

The settings that change the clipboard and DDE from public to private are
WIN_DDE and WIN_CLIPBOARD. Additional information can be found in Appendix A.
Settings

PMVIOP.DLL

This DLL has been modified to support the new clipboard and DDE settings.

Compiler Change

Three components of WIN-OS/2 have been changed to be compiled using the Watcom
Compiler. This provided a significant performance improvement for WIN-OS/2
sessions. The components are USER.EXE, GDI.EXE and WINSHELD.EXE.

DPMI Memory

Changes have been made in DPMI so that the Windows applications get access to
only the memory required to execute their application. This change was made by
having the DPMI layer only provide the memory requested by the applications,
rather than providing all the memory allocated for the session. The default
DPMI memory allocated to a WIN-OS/2 session has been changed to 64MB (from
4MB). This allows better used of system memory while providing access to large
amounts of memory when needed.

New Settings for WIN-OS/2

There are two new settings for WIN-OS/2 3.1. They are WIN_RUNMODE and
DOS_AUTOEXEC. WIN_RUNMODE changes the mode from enhanced to standard.
DOS_AUTOEXEC is used to specify a specific AUTOEXEC.BAT file for a session or
application. The appendix contains additional information.

Support for Windows 3.1 Printer Drivers

The additional support for Enhanced Mode Windows application also makes it
possible to use printer drivers designed for that level of support. These
drivers are primarily for the newer high end printers.


ΓòÉΓòÉΓòÉ 8. General Performance Optimizations ΓòÉΓòÉΓòÉ

Swap File Compaction

If the swap file extends beyond the initial size specified, OS/2 starts to
manage the swap file space. This will impact performance negatively because of
the associated overhead. OS/2 will attempt to shrink the swap file back to the
originally designated size. At that time, the additional system management is
discontinued by OS/2. The swap file grows and shrinks in 1 MB increments only.

The swap file shrinks when several conditions are met. When the amount of free
swap space in the swap file exceeds 1.5MB, swap file compaction will be
performed at system idle time. During compaction, free swap space will be moved
toward the end of the swap file. After compaction, when the amount of free
space at the end of the swap file is greater than 1 MB, the swap file will be
shrunk to make more disk space available to the user.

Caching Selectors

Changes were made in the OS/2 kernel (OS2KRNL) and the WIN-OS/2 kernel
(OS2K386.EXE) to cache selector information. This improves the performance of
loading applications and starting sessions.

Interrupt Descriptor Tables

The IDTs were aligned on paragraph boundaries (16 bytes) to optimize interrupt
code entry. This reduces the memory bus cycles required to vector to the
interrupt service routines. Placing the code on 16 byte boundaries also ensures
that the descriptor table is in the CPU cache on 80486 systems.

Code Basing

The major components of the system were based (as application .EXEs should be).
This allows the linker to do the internal fix-ups at link time, reducing load
time and memory requirements. Based components include the Workplace Shell,
display drivers, the graphics subsystem, DosCall1m PM WIN, SOM and the spooler.

Link Options

The link options used by the operating system components were reviewed.
Wherever possible code was packed with the linker /EXEPACK option. This reduced
the size of executable files requiring fewer disk accesses when loading the
code. Although the code must be unpacked at run time, this is faster than disk
access time. The /PACKCODE and /PACKDATA options were also used to reduce the
number of memory objects created. The /FARCALLTRANSLATION option was used to
let the linker change far calls to near calls whenever possible.

CTRL-ESC

The Control-Escape (CTRL-ESC) hot key sequence priority was raised to
Time-Critical to keep lower priority CPU intensive threads from locking out the
sequence.

Dynamic Time Slicing

OS/2 2.1 contains dynamic timeslicing. This means that OS/2 is adjusting the
timeslice values based on the actual processes active on the system. As the
workload changes, so will the timeslice handling. This change means that
earlier recommendations for TIMESLICE= values are no longer valid. Removing the
TIMESLICE= line in your CONFIG.SYS (if there) will enable dynamic timeslicing,
improving overall system performance.


ΓòÉΓòÉΓòÉ 9. Memory Reduction ΓòÉΓòÉΓòÉ

Although many new functions were added to OS/2 2.1, an several components were
converted to 32-bit, a concerted effort was made to reduce the base memory
requirements. Conversion to 32-bit code, without a special effort to reduce
memory requirements, will increase the working set for that code. Reduced
memory requirements translates into improved system performance. When more
memory is available, paging is reduced. Since disk operations are very slow
compared to CPU operations, the fewer needed the better the performance.

Memory can be reduced by fine tuning code, reducing redundant code and page
tuning. Page tuning is placing commonly used functions together in pages. This
was done by collecting information on the functions called to perform certain
tasks. The Real-time Tracing System (made by IBM, Yorktown Heights, NY) was
used for collection and verification. High use code was packed together in as
few pages as possible. Functions that work together were also packed together
in memory. The result is that the pages in memory when completing a task are
optimally packed to contain code that will most probably be used for the
completion of that task. Page tuning helped to reduce the overall working set
requirements for this release.

The following list summarizes the memory reduction items that were implemented
in OS/2 2.1:

o The base system resident memory pools, (heaps), were combined to reduce
  redundancy and reduce the size of the structures needed to manage each heap.

o The loader Module Table Entry (MTE) structures that were allocated on page
  (4K) boundaries were changed to be double word aligned.

o Code that was used to initialize the system and never used again is now
  discarded.

o Thunk interfaces were optimized to reduce overhead

o On a 4MB system the number of threads specified in the CONFIG.SYS THREADS=
  statement is reduced from 256 to 128.

o Several system components were page tuned, reducing working set memory
  requirements. This includes the Workplace Shell, the presen- tation manager
  display drivers, the spooler and the graphics engine.


ΓòÉΓòÉΓòÉ 10. VDM ΓòÉΓòÉΓòÉ

DOS mode has been improved by adding dual-threaded support, improvements to
DPMI, and by allowing customization of autoexecs per session.

Dual-Threaded DOS

Dual-thread support has been added to DOS sessions. OS/2 enhanced its
multimedia support with this feature. Multimedia programs need to handle
interrupts while doing file I/O. In OS/2 2.0, each VDM executes as one thread.
If the thread is busy doing a file I/O operation, it will not receive any
interrupt until the entire I/O operation is complete. By introducing a second
thread in OS/2 2.1, interrupts can be serviced while waiting for the completion
of the I/O operation. This improves the performance of multimedia DOS
applications, which need interrupt notification even when doing file I/O.

To set up a DOS application to use dual-threads, enable the DOS setting
INT_DURING_IO. It consumes more memory and CPU time when set ON. Only use it
when required. DOS communication programs that do file I/O will be helped by
this feature also.

DPMI enhancements

DPMI is a protected mode programming interface for DOS applications allowing
these applications to run in protect mode, while utilizing the real mode
services of the operating system and device drivers. In OS/2 2.1 the DPMI
support has been upgraded to version 1.0.

Customized AUTOEXEC.BAT files

The OS/2 CONFIG.SYS file specifies the operating system configuration and
installs device drivers and other memory resident applications. The OS/2
AUTOEXEC.BAT file is specific to the DOS session. OS/2 2.1 supports multiple
AUTOEXEC.BAT files, with each session specifying its AUTOEXEC.BAT.


ΓòÉΓòÉΓòÉ 11. Other ΓòÉΓòÉΓòÉ

Printing

For parallel ports LPT1 to LPT3, both parallel port device drivers, PRINT02.SYS
for Micro Channel machines and PRINT01.SYS for ISA and EISA machines, now send
data faster. This allows the print buffer, found on most printers, to be filled
quicker reducing the overall print job time.

Communication

Improvements were made in VPIC & VCOM to reduce code paths to improve
performance in OS/2 2.1. This means that OS/2 2.1 performs better running DOS
and Windows communication applications. OS/2 2.1 can support more DOS
communication applications due to these performance improvements.

Advanced Power Management

On laptops that support the Advanced Power Management 1.0 Specification, there
is an improvement in battery life. Software support will automatically be
installed on systems with the correct hardware support. The object icon can be
found in the System Setup folder.
This object is used to show the current status/state of your laptop's battery
and allows turning the advanced power management functions on and off.


ΓòÉΓòÉΓòÉ 12. Installation ΓòÉΓòÉΓòÉ

There have been 2 major changes to installation in OS/2 2.1. Selection of the
destination drive for WIN-OS/2 support has been added, and WIN-OS/2 accessories
are selectable in 4 categories:

o Windows Support

   - Readme Files
   - Accessories
   - Screen Savers
   - Sound

Additionally, installation no longer asks for all disks at install time, but
only for disks that contain needed files. The WIN-OS/2 selections are only
available with Selectable Installation. The destination drive is any partition
available at installation time, The default is the same partition and OS/2
installation.

The Full Installation installs all features available with OS/2.

Preselected installation provides a general installation of OS/2 features for
users. This default is good for new users that do not have enough space for a
full install. The features provided when the preselected installation is taken
include all required files for OS/2 and the following features:

o OS/2 Tutorial
o Fonts (not including Helvetica or Courier(outline))
o Optional System Utilities (not including backup & restore, Fdiskpm, PM REXX
  and Sort.
o Tools and Games (not including Search and Scan or Personal Productivity)
o OS/2 DOS and Windows Support
o REXX
o Serviceability and Diagnostic Aids
o Optional Bitmaps

The Selectable Install allows end users to choose which options to install.

Full installation option installs all features of OS/2. This selection requires
about 40 MB of disk space. Additional space is required for the swap file in
constrained systems. If your partition is small ( < 50 MB) it is advisable to
move the swap file to another partition.

The features provided when the full installation is taken include all required
files for OS/2 and ALL the features available for your hardware.


ΓòÉΓòÉΓòÉ 13. Summary ΓòÉΓòÉΓòÉ

In summary, you should see generally improved performance in OS/2 version 2.1.
Major improvement will be seen in the performance of Windows applications in
the WIN-OS/2 session.


ΓòÉΓòÉΓòÉ 14. Appendix A. Settings ΓòÉΓòÉΓòÉ

The following is a summary of the settings referred to in this document.

o WIN_DDE

  This setting allows WIN-OS/2 to share DDE information between WIN-OS/2 and
  OS/2 sessions. For better performance, this setting should be set OFF, but
  only if you are not exchanging data via DDE between OS/2 and WIN-OS/2
  applications. This should be set to Off  for private data exchange between
  DOS applications.

  The default is ON.

o WIN_CLIPBOARD

  This setting allows WIN-OS/2 to share clipboard information between public
  WIN-OS/2 and OS/2 sessions.

  For better performance this setting should be set to Off  for private data
  exchange between WIN-OS/2 applications. Only set this setting Off if you will
  not be exchanging clipboard data between OS/2 applications and WIN-OS/2
  applications.

  The default is ON.

o WIN_RUNMODE

  In WIN-OS/2 3.1, the WIN_RUNMODE Settings option has been changed to include
  two radio buttons for selection either one of the two modes-- 3.1 Standard or
  3.1 Enhanced Compatibility. Select the button 3.1 Standard for applications
  to be run in Standard mode

  The default is Standard.

o DOS_AUTOEXEC

  The DOS_AUTOEXEC setting is new in WIN-OS/2 3.1. This setting allows the
  application to run in different DOS environments. You can now specify the
  AUTOEXEC.BAT file to be executed when the VDM session is started.

  The default is blank.

o INT_DURING_IO

  Allows interrupts to be handled during file reads/writes. This setting is
  primarily designed for DOS multimedia applications and should be turned On
  when the user runs multimedia applications. Other DOS applications that do
  not require long file read/write should leave it Off  as it will cost more
  memory and system overhead.

  The default value is Off.

o DOS_AUTOEXEC

  The DOS_AUTOEXEC setting is new in OS/2 2.1. It allows setting a specific
  AUTOEXEC.BAT file for each DOS session.or Customized AUTOEXEC.BAT files help
  to reduce memory while optimizing function.

  The default is the AUTOEXEC.BAT file in the root directory.