KB102985 - REG: CurrentControlSet Entries PART 2: SessionManager

The article contains REGISTRY entries for the CurrentControlSet\Control Subkeys Part 2--Session Manager entries.

For listings of the other control subkeys under CurrentControlSet, see the articles:

CurrentControlSet Part 1, containing:

BootVerificationProgram
ComputerName
DisplayDriver
GroupOrderList
HiveList
KeyboardLayout
Lsa
NetworkProvider
Nls
PriorityControl
ProductOptions
ServiceGroupOrder

and

CurrentControlSet Part 3, containing:

Setup
TimeZoneInformation
VirtualDeviceDrivers
Windows
WOW

CURRENTCONTROLSET\CONTROL SUBKEYS ENTRIES

This key contains parameters that control system startup, such as subsystems to load, the size and location of paging files, and so on.

NOTE: The system must be restarted for any changes in the Control key to take effect.

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

Default:   autocheck autochk *

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

CriticalSectionTimeout REG_DWORD

Default:   0x278d00

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

GlobalFlag REG_DWORD

Default:   0x21100000

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.

ObjectDirectories REG_MULTI_SZ

Default:   \DosDevices
           \Windows
           \RPC Control

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

RegisteredProcessors REG_DWORD

Default:   0x4

ResourceTimeoutCount REG_DWORD

Default:   0x9e340

The number of 4-second ticks that need to transpire before a resource time- out occurs. Retail installations of Windows NT will never time-out.

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 key have the data type of REG_SZ. The following list shows the default entries under this key.

   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 applications.

The Registry path for these values is:

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

ComSpec REG_EXPAND_SZ Filename

Default: %systemRoot%\SYSTEM32\CMD.EXE

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

Os2LibPath REG_EXPAND_SZ Filename

Default: %systemRoot%\SYSTEM32\os2\dll

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

Path REG_EXPAND_SZ Filename

Default: %systemRoot%\SYSTEM32; %SystemRoot%

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

Windir REG_EXPAND_SZ Filename

Default: %systemRoot%\SYSTEM32\CMD.EXE

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

FileRenameOperations Entries

Entries for the FileRenameOperation support the MoveFileEx delayed-rename and delayed-delete capabilities. Entries are stored under this Registry path:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet
   \Control\Session Manager\FileRenameOperations

These entries should be maintained only by the system.

KnownDLLs Control Entries

The KnownDlls key 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

Default: 512K

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.

LargeSystemCache REG_DWORD Number

Default: 0

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 Advanced Server installation base.

NonPagedPoolSize REG_DWORD Number of bytes

Default: 0

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.

PagedPoolSize REG_DWORD 0 to 128 MB

Default:   0x3000000 (32 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.

PagingFiles REG_MULTI_SZ System_Paging_Files

Default: C:\pagefile.sys 27

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

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

Default: Os2 Posix

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

Os2 REG_EXPAND_SZ Path and filename

Default:  %SystemRoot%\system32\os2ss.exe

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

Posix REG_EXPAND_SZ Path and filename

Default:  %SystemRoot%\system32\psxss.exe

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

Required REG_MULTI_SZ Name

Default: Debug Windows

Windows REG_EXPAND_SZ Path and filename

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

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

Reference: "The Windows NT Resource Kit for Operating System Version 3.1".