Terminal Server Client Connections and Logon Limited by MaxWorkItem and MaxMpxCt Values

• Microsoft Windows NT Server versions 4.0, 4.0 SP4, Terminal Server Edition

SYMPTOMS

After multiple Terminal Server clients establish a session with a server running Windows NT Server 4.0, Terminal Server Edition, additional clients are unable to connect. When this occurs, in some cases, clients are not able to browse certain servers or domain controllers after a specific number of client sessions have been established. They may not exhibit the same symptoms as above, but this issue may be corrected by the solution below.

This behavior is not affected by either the number of licenses in place or the License Logging Service on either the Terminal Server computer or domain controller. This problem can occur with either Independent Computing Architecture (ICA) or Remote Desktop Protocol (RDP) clients, and the clients may receive one of the following error messages:

System could not log you on because domain <domainname> is not available

You do not have access to logon to this session

Error 1727: The remote procedure call failed and did not execute

-or-

Event ID: 1311
Source: NetLogon
Description: There are currently no logon servers available to service the logon request.

Error 1722: The RPC server is unavailable.

Error 1723: The RPC server is too busy to complete this operation.

Error 1721: Not enough resources are available to complete this operation.

RESOLUTION

To resolve this issue, you need to either edit the existing values or add the following registry entries for both MaxWorkItems and MaxMpxCt to the Terminal Server computers configured as a domain controller. By default, MaxWorkItems and MaxMpxCt do not appear under the parameters key although they are in effect.

NOTE: These values need to be added with such a ratio that the value for MaxWorkItems is at least four times as large as that for MaxMpxCt. For example, if MaxMpxCt has a value of 1024, then MaxWorkItems needs to have a value of at least 4096.
WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

1. Start Registry Editor (Regedt32.exe).



2. Locate the following key in the registry:

   
   HKEY_LOCAL__MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters 




3. Double-click the MaxWorkItems value, type 4096, click Decimal, and then click OK.
   
   The number value you enter is arbitary, and you could also enter 1024, 2048, 8192, or 16384 if desired. However it is recommended to begin at the lower levels and work up as needed, doubling the value each time. The range for this value is 1 through 65535. If this value already exists, but you are experiencing problems similar to those outlined above, then edit this entry and double its current value; For example, if it shows a value of 1012, then change it to 2024, and so forth. If problems persist, then continue this process until the issue subsides.
   
   NOTE: This value needs to be at least four times as large as MaxMpxCt.



4. If the MaxWorkItems value does not exist in the Parameters key, on the Edit menu, click Add Value, and then add the following registry value:

   
      Value Name: MaxWorkItems
      Data Type:  REG_DWORD
      Value:      4096 




5. Double-click the MaxMpxCt value, type 1024, click Decimal, and then click OK.
   
   The default value for MaxMpxCt is 50, but remember that MaxWorkItems needs to be set at least 4 times as high as the number used for MaxMpxCt.
   
   NOTE: Windows 95 and Windows 98 clients can interpret this registry entry differently than Windows NT, so apply this value according to which client is being used. For more information about how Windows 95 and Windows 98 does this, please click the article number below to view the article in the Microsoft Knowledge Base:

   Q232890 Win98 Fails to connect to NT4 share -- net client hangs.




6. If the MaxMpxCt value does not exist in the Parameters key, on the Edit menu, click Add Value, and then add the following registry value:

   
      Value Name: MaxMpxCt
      Data Type:  REG_DWORD
      Value:      1024 (Decimal) 

   When you add this value to the registry of a computer running Windows 95 or Windows 98, set this value at either 510 Decimal (or 1fe Hex).


NOTE: If Windows 95, Windows 98, and Windows NT clients are present, then the value for MaxMpxCt should be set to the default used for Windows95 and Windows 98, because Windows NT should read the value without problems.
7. Quit Registry Editor and restart the computer.

MORE INFORMATION

Default MaxWorkItems Value

Default MaxMpxCt values

Q191370 Slow Network Performance with Terminal Server

Additional query words: Lock Freeze hang logging

Keywords : kbenv kbnetwork
Version : winnt:4.0,4.0 SP4
Platform : winnt
Issue type : kbprb