Session Manager Control Entries

The Session Manager subkey contains the global variables used by the Session Manager. These values are stored under the following Registry path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager

BootExecute REG_MULTI_SZ

Specifies programs to run during startup. For example, if CONVERT.EXE has been used to convert the file system on a hard disk drive, this value is added to BootExecute so that conversion occurs when the system is restarted:

   BootExecute = autocheck autoconv \DosDevices\x: /FS:NTFS

Default: autocheck autochk *

CriticalSectionTimeout REG_DWORD

Specifies the deadlock time-out for critical sections. Usually, retail installations of Windows NT will not time-out and detect deadlocks.

Default: 0x278d00

GlobalFlag REG_DWORD

Controls various Windows NT internal operations. You can change this value to disable the OS/2 subsystem if you want to run bound applications in a VDM, rather than under the OS/2 subsystem. Set this value to 20100000 to disable the OS/2 subsystem.

Default: 0x21100000

ObjectDirectories REG_MULTI_SZ

Lists the object directories to create during startup. Do not edit these entries.

Default: \DosDevices
\Windows
\RPC Control

DOS Devices Control Entries

The DosDevices subkey lists the built-in symbolic links to create at startup. The values are stored under this subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet
    \Control\Session Manager\DOS Devices

Entries in this subkey have the data type of REG_SZ. The following list shows the default entries under this subkey.

AUX=\DosDevices\COM1
MAILSLOT=\Device\MailSlot
NUL=\Device\Null
PIPE=\Device\NamedPipe
PRN=\DosDevices\LPT1
TELNET=\Device\Telnet
UNC=\Device\Mup

Environment Control Entries

The Environment subkey defines environment variables that the system creates and that are used by Windows NT Logon and Program Manager.

Caution Use extreme care in changing these entry values. If the operating system cannot find the files specified for a subsystem, you will not be able to run non-Windows NT-based applications.

The Registry path for these values is the following:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet
    \Control\Session Manager\Environment

ComSpec REG_EXPAND_SZ Filename

Defines the path and filename for the Windows NT command interpreter (the equivalent of MS-DOSCOMMAND.COM in MS-DOS).

Default: %systemRoot%\SYSTEM32\CMD.EXE

Os2LibPath REG_EXPAND_SZ Filename

Defines the path for the Microsoft OS/2 version 1.x library.

Default: %systemRoot%\SYSTEM32\os2\dll

Path REG_EXPAND_SZ Filename

Defines the path variable for Windows NT logon and Program Manager.

Default: %systemRoot%\SYSTEM32; %SystemRoot%

Windir REG_EXPAND_SZ Filename

Defines the path for the executable for WOW, as used by Windows NT logon and Program Manager.

Default: %systemRoot%\SYSTEM32\CMD.EXE

KnownDLLs Control Entries

The KnownDlls subkey defines the set of DLLs that are first searched during system startup. In general, these are system DLLs that are loaded from disk into a section of memory and are checked for integrity. These DLLs consume some resources, even if no application loads them. These appear as separate entries under this Registry path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\KnownDLLs

driverName REG_SZ DLL Filename

This series of entries defines a driver name and the corresponding DLL filename. The following shows the default entries:

advapi32=advapi32.dll	olecli32=olecli32.dll
comdlg32=comdlg32.dll	olesvr32=olesvr32.dll
crtdll=crtdll.dll	rpcrt4=rpcrt4.dll
DllDirectory=%SystemRoot%\system32	shell32=shell32.dll
gdi32=gdi32.dll	user32=user32.dll
kernel32=kernel32.dll	version=version.dll
lz32=lz32.dll

Memory Management Control Entries

The Memory Management subkey defines paging options under the following Registry path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control
    \Session Manager\Memory Management

The paging file parameters should be defined by using the System icon in Control Panel and choosing the Virtual Memory button.

IoPageLockLimit REG_DWORD Number of bytes

Specifies the limit of the number of bytes that can be locked for I/O operations. When this value is 0, the system uses the default (512K). The maximum value is about the equivalent of physical memory minus pad, which is 7 MB for a small system and grows as the amount of memory grows. For a 64 MB system, pad is about 16 MB; for a 512 MB system, pad is about 64 MB.

Default: 512K

LargeSystemCache REG_DWORD Number

Specifies, for a nonzero value, that the system favor the system-cache working set rather than the processes working set. Set this value by choosing the Windows NT ServerWindows NT Server installation base.

Default: 0

NonPagedPoolSize REG_DWORD Number of bytes

Specifies the size of nonpaged pool in bytes. When this value is 0, the system uses the default size (based on physical memory). The maximum amount is about 80 percent of physical memory.

Default: 0

PagedPoolSize REG_DWORD 0 to 128 MB

Specifies the size of paged pool in bytes. When this value is 0, the system uses the default size (32 MB). See also the entry for RegistrySizeLimit at the beginning of this section.

Default: 0x3000000 (32 MB)

PagingFiles REG_MULTI_SZ System_Paging_Files

Specifies page file information set by choosing the System icon in Control Panel.

Default: C:\pagefile.sys 27

Subsystem Startup Control Entries

The following is the Registry path for the subsystem settings established at startup:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet
    \Control\Session Manager\SubSystems

These values should only be maintained by the system. You should not need to manually define these settings.

Debug REG_EXPAND_SZ Names

Default: (no value)

Optional REG_MULTI_SZ Subsystem names

Defines subsystems that are only loaded when the user starts an application that requires this subsystem.

Default: Os2 Posix

Os2 REG_EXPAND_SZ Path and filename

Defines the path to the executable file used to start the Microsoft OS/2 version 1.x subsystem.

Default: %SystemRoot%\system32\os2ss.exe

Posix REG_EXPAND_SZ Path and filename

Defines the path to the executable file used to start the POSIX subsystem. (There are no additional POSIX entries in the Registry.)

Default: %SystemRoot%\system32\psxss.exe

Required REG_MULTI_SZ Name

Default: Debug Windows

SystemPages REG_DWORD Number of entries

Defines the number of system page table entries reserved for mapping I/O buffers and other information into the system address space. Each entry maps a single page. The value 0 indicates that the default number of entries is to be used.

Default: TBD

Windows REG_EXPAND_SZ Path and filename

Defines the path to the executable file used to start the Win32 subsystem.

Default: %SystemRoot%\system32\csrss.exe ObjectDirectory=\Windows SharedSection=1024,3072 Windows=On SubSystemType=Windows ServerDll=basesrv,1 ServerDll=winsrv:GdiServerDllInitialization,4 ServerDll=winsrv:UserServerDllInitialization,3 ServerDll=winsrv:ConServerDllInitialization,2 ServerDll=mmsndsrv,5 ProfileControl=Off MaxRequestThreads=16