REG: CurrentControlSet Entries PART 2: SessionManager

This article was previously published under Q102985
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The article contains REGISTRY entries for the CurrentControlSet\ControlSubkeys Part 2--Session Manager entries.

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

CurrentControlSet Part 1, containing:

  • BootVerificationProgram
  • ComputerName
  • DisplayDriver
  • GroupOrderList
  • HiveList
  • KeyboardLayout
  • Lsa
  • NetworkProvider
  • Nls
  • PriorityControl
  • ProductOptions
  • ServiceGroupOrder
CurrentControlSet Part 3, containing:

  • Setup
  • TimeZoneInformation
  • VirtualDeviceDrivers
  • Windows
  • WOW


This key contains parameters that control system startup, such assubsystems 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 totake effect.


The Session Manager subkey contains the global variables used by theSession 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 hasbeen used to convert the file system on a hard disk drive, this value isadded to BootExecute so that conversion occurs when the system isrestarted: BootExecute = autocheck autoconv \DosDevices\x: /FS:NTFS

CriticalSectionTimeout REG_DWORD

Default:   0x278d00		
Specifies the deadlock time-out for critical sections. Usually, retailinstallations 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 valueto disable the OS/2 subsystem if you want to run bound applications in aVDM, rather than under the OS/2 subsystem. Set this value to 20100000 todisable the OS/2 subsystem.

ObjectDirectories REG_MULTI_SZ

Default:   \DosDevices           \Windows           \RPC Control		
Lists the object directories to create during startup. Do not edit theseentries.

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 atstartup. 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 showsthe 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 systemcreates and that are used by Windows NT Logon and Program Manager.

CAUTION: Use extreme care in changing these entry values. If the operatingsystem cannot find the files specified for a subsystem, you will not beable 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 (theequivalent 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 logonand Program Manager.

FileRenameOperations Entries

Entries for the FileRenameOperation support the MoveFileEx delayed-renameand delayed-delete capabilities. Entries are stored under this Registrypath:
   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 duringsystem startup. In general these are system DLLs that are loaded from diskinto a section of memory and are checked for integrity. These DLLs consumesome resources, even if no application loads them. These appear as separateentries 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 DLLfilename. 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 followingRegistry path:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet   \Control\Session Manager\Memory Management		
The paging file parameters should be defined by using the System icon inControl 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/Ooperations. When this value is 0, the system uses the default (512K). Themaximum value is about the equivalent of physical memory minus pad, whichis 7 MB for a small system and grows as the amount of memory grows. For a64 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-cacheworking set rather than the processes working set. Set this value bychoosing 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, thesystem uses the default size (based on physical memory). The maximum amountis 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 systemuses the default size (32 MB). See also the entry for RegistrySizeLimit atthe 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 ControlPanel.

Subsystem Startup Control Entries

The following is the Registry path for the subsystem settings establishedat startup:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet   \Control\Session Manager\SubSystems		
These values should only be maintained by the system. You should not needto manually define these settings.


Default: (no value)		

Optional REG_MULTI_SZ Subsystem names

Default: Os2 Posix		
Defines subsystems that are only loaded when the user starts an applicationthat 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/2version 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.exeObjectDirectory=\Windows SharedSection=1024,3072Windows=On SubSystemType=Windows ServerDll=basesrv,1ServerDll=winsrv:GdiServerDllInitialization,4ServerDll=winsrv:UserServerDllInitialization,3ServerDll=winsrv:ConServerDllInitialization,2ServerDll=mmsndsrv,5 ProfileControl=OffMaxRequestThreads=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".

Article ID: 102985 - Last Review: 12/04/2015 09:38:32 - Revision: 2.1

Microsoft Windows NT Advanced Server 3.1, Microsoft Windows NT Workstation 3.1, Microsoft Windows NT Advanced Server 3.1

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