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REG: CurrentControlSet Entries PART 2: SessionManager
Article ID: 102985 - View products that this article applies to.
This article was previously published under Q102985
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:
andCurrentControlSet Part 3, containing:
CURRENTCONTROLSET\CONTROL SUBKEYS ENTRIESThis 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 ENTRIESThe Session Manager subkey contains the global variables used by the Session Manager. These values are stored under the following Registry path:
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 *
Specifies the deadlock time-out for critical sections. Usually, retail installations of Windows NT will not time-out and detect deadlocks.
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.
Lists the object directories to create during startup. Do not edit these entries.
Default: \DosDevices \Windows \RPC Control
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 EntriesThe DosDevices subkey lists the built-in symbolic links to create at startup. The values are stored under this subkey:
Entries in this key have the data type of REG_SZ. The following list shows the default entries under this key.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet \Control\Session Manager\DOS Devices
AUX=\DosDevices\COM1 MAILSLOT=\Device\MailSlot NUL=\Device\Null PIPE=\Device\NamedPipe PRN=\DosDevices\LPT1 TELNET=\Device\Telnet UNC=\Device\Mup
Environment Control EntriesThe 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
Defines the path and filename for the Windows NT command interpreter (the equivalent of MS-DOS COMMAND.COM).
Os2LibPath REG_EXPAND_SZ Filename
Defines the path for the Microsoft OS/2 version 1.x library.
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.
FileRenameOperations EntriesEntries for the FileRenameOperation support the MoveFileEx delayed-rename and delayed-delete capabilities. Entries are stored under this Registry path:
These entries should be maintained only by the system.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet \Control\Session Manager\FileRenameOperations
KnownDLLs Control EntriesThe 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 FilenameThis 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 EntriesThe Memory Management subkey defines paging options under the following Registry path:
The paging file parameters should be defined by using the System icon in Control Panel and choosing the Virtual Memory button.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet \Control\Session Manager\Memory Management
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.
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 Advanced Server installation base.
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.
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 EntriesThe following is the Registry path for the subsystem settings established at startup:
These values should only be maintained by the system. You should not need to manually define these settings.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet \Control\Session Manager\SubSystems
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.
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.)
Required REG_MULTI_SZ Name
Default: Debug Windows
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
Reference: "The Windows NT Resource Kit for Operating System Version 3.1".