Macintosh Clients Connected to WinNT Server Appear to Hang

• Microsoft Windows NT Server versions 3.51 and 4.0

SYMPTOMS

Any application that uses the AFP command CatSearch, such as the Macintosh File Find, may reduce the server's responsiveness to other Macintosh clients on the network, causing them to appear to stop responding for a brief period of time.

This problem will only occur when there are a large number of Macintosh clients on the network and the Macintosh volume on the Windows NT server contains a very large number of directories and files.

CAUSE

In Windows NT 3.51, support for the AFP CatSearch command was added. This command is used so the Macintosh client asks the server to do the search, rather than performing the search of the Macintosh volume itself. CatSearch instructs Windows NT to look through all directories and files, based on the specified search parameters. When this search is performed at the root of a Macintosh volume with many directories, subdirectories, and files, it can delay the processing of requests from other Macintosh clients and the Macintosh clients will appear to stop responding while they wait for their request to be processed.

RESOLUTION

To Disable CatSearch for a particular SFM volume:

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.

1. Install the Windows NT 4.0 Service Pack 2.

2. Run Rededt32.exe and go to the following registry location:

        HKLM\System\CurrentControlSet\Services\MacFile\Parameters\Volumes
   

3. Select the volume on which you want to disable CatSearch, and then select Multi String from the Edit menu.

4. Add "DisableCatsearch=1" without the quotes.

5. Exit the registry editor, and then stop and restart Services for Macintosh.

STATUS

Microsoft has confirmed this to be a problem in Windows NT versions 3.51 and 4.0. This problem was corrected in the latest Microsoft Windows NT 4.0 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K

MORE INFORMATION

How AFP CatSearch Works

There are several ways Macintosh clients search a remote volume. One way is to use Enumerate, which looks similar to Microsoft’s FindFirst, FindNext, which is a client-based search. This method puts responsibility on the client (and some stress on the network). Another way is for a client to send a server-based command, CatSearch, which puts all of the responsibility and stress on the server. This method is used by most Macintosh applications, such as the FindFile utility, by default. This command, in effect, makes the Services for Macintosh (SFM) server do the file search on behalf of the client. The way SMF is designed on Windows NT, other users are locked out of the volume until the search is complete. If the Macintosh volume has a large number of directories and files (number of directories makes a bigger impact), and the search is started at or near the root of the volume, the search may impact other users. This becomes an issue because of the way the Macintosh operating system performs network I/O. The Macintosh uses synchronous calls to the network, and any delay in response from the server causes the Macintosh to stop responding. The Macintosh File Find interface allows users to search sub-directories, but the default is the entire volume and the other option isn't very obvious. This causes most file searches from the Macintosh to be done on the entire volume. If applications and users were more selective, file look-ups would not impact the system.

Possible Affect of Disabling AFP CatSearch on the Server

When the AFP CatSearch command is disabled, Macintosh clients may experience long delays when performing Find File from the Macintosh desktop. The delays can be significant. A Windows NT server performing the AFP CatSearch request may lock the SFM volume for only a few moments, but when AFP CatSearch is disabled, a client may take several minutes, or more, to complete the same task. When disabling the AFP CatSearch command, users are advised that, if they do initiate a Find File, they may expect delays or long hangs while the Macintosh is performing this task.

If a Find File is used with care, then disabling the CatSearch may become unnecessary. Users who need to perform the Find File should narrow down their choices to a few directories, rather than searching an entire volume. Also, extremely large volumes with lots of subfolders can increase the problem. If the File Find is being used constantly to access information, consider using a text file with the path to the needed file or a database that keeps a list of files in a particular volume. These methods can significantly improve server response.