"The network BIOS command limit has been reached" error message in Windows Server 2003, in Windows XP, and in Windows 2000 Server

CAUSE:
This issue may occur if the following conditions are true:

• This issue may occur if the client computer submits simultaneous, long-term requests against a file server that uses the Server Message Block (SMB) protocol. An example of a long-term request is when a client computer uses the FindFirstChangeNotification function to monitor a server share for changes.
• This issue may occur if the MaxCmds registry value setting on the client is less than 50, or the MaxMpxCtregistry value setting on the server is less than 50.
  
  Note The MaxMpxCt registry value setting may have a different name on other SMB/CIFS implementations. The Common Internet File System (CIFS) specification refers to it as MaxMpxCount.

RESOLUTION:

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756  How to back up and restore the registry in Windows

To resolve this issue, verify that the MaxCmds and MaxMpxCt registry values are set to 50 or more. To do this, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following key in the registry:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanworkstation\parameters
3. In the right pane, double-click the MaxCmds value.
4. In the Value data box, verify that the value is 50 or more.
   
   Note In a Microsoft Windows Terminal Services environment, you may have to set the MaxCmds registry value to 500 or more. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
   232476  Terminal Server client connections and logon limited by MaxWorkItem and MaxMpxCt values
5. Locate and then click the following key in the registry:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters
   Note Make sure that you make this change to the lanmanserver\parameters registry key and not to thelanmanworkstation\parameters registry key mentioned in step 2.
6. In the right-pane, double-click the MaxMpxCt value.
   
   Note On SMB servers that are running a version of Windows earlier than Windows 2000, the MaxMpxCt registry entry is named MaxMpxCount, but has the same function.
7. In the Value data box, verify that the value is 50 or more. 
   
   Note The MaxMpxCt value determines the maximum number of simultaneous, active requests that the server permits from an individual client.
8. Quit Registry Editor.
9. Restart the server.

Note The MaxCmds and MaxMpxCt registry entries are REG_DWORD decimal entries. If they do not exist on your computer, you can create them as new REG_DWORD values. The range of values for these registry entries is between 0 and 65535.

MORE: 

The maximum number of simultaneous, active requests between an SMB client and the server is determined when a client/server session is negotiated. The maximum number of requests that a client supports is determined by theMaxCmds registry value. The maximum number of requests that a server supports is determined by the MaxMpxCtregistry value. For a particular client and server pair, the number of simultaneous, active requests is the lesser of these two values.

In a BizTalk environment, add both registry values to the BizTalk server and the remote UNC Share server. 

To track the number of simultaneous, active requests on an SMB client, add the Current Commands counter in the SMB Redirector performance object to Performance Monitor.