Useful Registry Keys

The first bulleted list displays registry keys that you can use to change the behavior of the system services. The second bulleted list shows some miscellaneous registry keys and descriptions that you can modify to change your system configuration.

I have not included all of the keys that are available. For those of you who want more information, I suggest purchasing the Windows NT Workstation Resource Toolkit. The toolkit includes a help file that contains most, but not all, of the information contained in the following lists (some information included in the lists is based on my experience working with Windows NT Server and may not be documented in the Resource Kit).

System service configuration registry keys:

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Server\Parameters\InitConTable
This value’s data is used to set the initial number of tree connections to be allocated in the connection table. The server service automatically increases this value as needed. However, setting this value to a higher setting initially can improve performance because the overhead involved to increase this setting is costly. The minimum is 1, the maximum is 128, and the default is 8.

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Server\Parameters\InitFileTable
\tab This value’s data entry specifies the initial number of file entries to be pre- allocated in the file table of each server connection. Set this to a higher value if your users use a higher number of files on a frequent basis. The server service will automatically adjust the number of file table entries upward if needed. However, pre-allocating them will improve performance. The minimum is 1, the maximum is 256, and the default is 16.

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Server\Parameters\ThreadCountAdd
This value’s data specifies how many threads per processor that a server service should use. Increasing this value can increase performance, but it will require additional memory. The minimum is 0, the maximum is 10, and the default depends on the system configuration (generally 1).

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Server\Parameters\ThreadPriority
Specifies the server thread priorities in relation to the base priority of the server process. Increasing this value can improve server performance at the cost of interactive responsiveness. Values can be 0 (normal), 2 (background), 1 (foreground), and 15 (realtime). Setting the value to 15 is not really a good idea as the server threads will then consume the majority of CPU cycles. The default is 1.

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Server\Parameters\Hidden
Set this value’s data entry to 1 to hide a server from client browse requests on the network. Users will not see this as an available resource, but they can still connect to the network if they know the server name and resource name. Set the value to 0 (default) to allow the server to be visible in browse requests.

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Server\Parameters\SizReqBuf
Set this value’s data to a higher value to increase performance at the cost of local memory. The minimum is 512, the maximum is 65536, and the default is 4356 (all in bytes).

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Workstation\Parameters\MaxCmds
This value’s data specifies the number of work buffers that the redirector will reserve. Increasing this value may increase performance. The minimum is 0, the maximum is 256, and the default is 15.

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Workstation\Parameters\MaxCollectionCount
Increasing this value above the default of 16 will buffer writes to character-mode named pipes less than this value. The minimum is 0, and the maximum is 65536. Note: changing this value will not affect SQL Server performance.

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Workstation\Parameters\CollectionTime
Increasing this value above the default of 250 may improve the performance of named pipe applications. The minimum is 0, and the maximum is 65535000 milliseconds. Note: changing this value will not affect SQL Server performance.

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Workstation\Parameters\SizCharBuf
This value’s data entry specifies the maximum number of bytes that will be written to a character-mode named pipe. Increasing this value may improve performance of named pipe applications, but will also affect SQL Server performance. The minimum is 64, the maximum is 4096, and the default is 512 (in bytes).

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanman Workstation\Parameters\MailslotBuffer
If your application is losing mailslot messages, increase this value above the default of 5 buffers.

•  HKEY_LOCAL_MACHINE\SYSTEM\Print\Printers\Printer Name\SpoolDirectory
Set this value to the directory you wish to use for all of your printer spooling for a specific printer. Note: The Printer Name entry is a placeholder for the name of the printer you installed (for example, HP DeskJet 310).

Miscellaneous registry keys:

•  HKEY_LOCAL_MACHINE\SOFTWARE\WindowsNT\CurrentVersion\ Winlogon\ShutdownWithoutLogon
Set this value to 1 to add the Shutdown button to the Logon dialog so that anyone can shut down the server without logging on to the system. Set this value to 0 (default) to require a log on to the system in order to shut down the system.

•  HKEY_LOCAL_MACHINE\SOFTWARE\WindowsNT\CurrentVersion\ Winlogon\LegalNoticeCaption
Set this value’s data string to the text you want displayed in a message box whenever a user logs on locally to the system. Use this as a disclaimer to protect yourself from unauthorized users. In order to make this message box visible, you must also set LegalNoticeText to a non-null value.

•  HKEY_LOCAL_MACHINE\SOFTWARE\WindowsNT\CurrentVersion\ Winlogon\LegalNoticeText
Set this value’s data string to the text you want displayed in the caption bar of the message box whenever a user logs on to the system. In order to make this message box visible, you must also set LegalNoticeCaption to a non-null value.

•  HKEY_LOCAL_MACHINE\SOFTWARE\WindowsNT\CurrentVersion\ Winlogon\AutoAdminLogon
Set this value’s data to 1 to automatically log on to the system and bypass the logon dialog. Set it to 0 to restore the original settings and require a user to log on via the logon dialog box. In order to perform this action, you will need to create the above value with the Registry Editor with a data type of REG_SZ. This value must be used in conjunction with the DefaultUserName and DefaultPassword values.

•  HKEY_LOCAL_MACHINE\SOFTWARE\WindowsNT\CurrentVersion\ Winlogon\DefaultPassword
Set this value’s data to the password for the user name you want to use to automatically log on to the system and bypass the logon dialog. In order to perform this action, you will need to create the value with the Registry Editor with a data type of REG_SZ. Note: This data value is unprotected and is visible to all users who log on to the system and can thereby obtain the user name and password. This value must be used in conjunction with the DefaultUserName and AutoAdminLogon values.

•  HKEY_LOCAL_MACHINE\SOFTWARE\WindowsNT\CurrentVersion\ Winlogon\DefaultUserName
Set this value’s data to the default user name you want to use in the automatic logon process. This value must be used in conjunction with the AutoAdminLogon and DefaultPassword values.

•  HKEY_LOCAL_MACHINE\SOFTWARE\WindowsNT\CurrentVersion\ IniFileMapping
This key contains information related to the mapping of configuration data entries. You will find references to USR (which specifies that the configuration information is contained in HKEY_CURRENT_USER) or SYS (which is a reference to the HKEY_LOCAL_MACHINE\SOFTWARE key). For example, the MSMAIL32.INI entry is USR:Software\Microsoft\Mail, which means that when Microsoft Mail starts, it will look in HKEY_CURRENT_USER\ Software\Mail for configuration data.

•  HKEY_LOCAL_MACHINE\SOFTWARE\WindowsNT\CurrentVersion\ SourcePath
Change this value’s data if you want to change the source media path, which is used to copy the device drivers whenever you add new hardware or software to your system. The preferred method is to use a UNC file name (such as \\SRV\CD-ROM\I386) instead of a mapped drive letter (such as E:\I386). Used in conjunction with WinntPath.

•  HKEY_LOCAL_MACHINE\SYSTEM\Setup\WinntPath
Change this value’s data if you want to change the source media path, which is used to copy the device drivers whenever you add new hardware or software to your system. The preferred method is to use a UNC file name (such as \\SRV\CD-ROM\I386) instead of a mapped drive letter (such as E:\I386). Used in conjunction with SourcePath.

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\RegisterProcessors
If you have a multiprocessor kernel installed on your system, you can change this value’s data to support more than the maximum (default) of four processors for Windows NT Server.

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WOW\ LPT_timeout
Change this value’s data from 15 (default) to increase the 16-bit Windows application printer timeout value if your 16-bit Windows application experiences printer timeout problems.

•  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WOW\ DefaultSeperateVDM
Set this value to 1 to have 16-bit Windows applications run in separate address spaces by default. Set it to 0 (default) to use a shared address space.

Summary

In this chapter, you learned the basics of the registry. You learned where Windows NT Server stores specific information and how to navigate the registry. You learned how to protect your registry by setting permissions and enabling auditing on specific registry keys. You also explored the basics about how to repair a damaged registry. These abilities will stand you in good stead as you perform your day-to-day administrative duties. More importantly, the registry contains all of the configuration information on your computer. If you just spend some time browsing the registry, you can learn quite a bit about the underlying mechanics of Windows NT Server. Just remember the cardinal rule, “Don’t change what you do not understand”. At least not without making a backup first!