Redirector Problems and Other Network Problems

Last reviewed: 03/12/2007
Article ID: R10200

Summary

When application software is deployed on a network, any shortcomings or weaknesses in the operating system or network are inherited by the application. As a result, when network problems occur, they affect the application software. Because the problems appear to occur in the application software, frequently the application software is blamed. However, data corruption and problems that are manifested in the application software are quite often the fault of problematic networking software (and sometimes hardware issues). As the number of users increase, so does the network traffic and so can the frequency of any underlying problems. Because of the complexity of a networking system, when data corruption occurs, it can be very difficult to diagnose and troubleshoot problems, even for trained specialists. 

This document is a white paper that was written to educate our customers, dealers and other third parties about the various problems associated with networks and redirectors that we have encountered on a regular basis. This document also discusses diagnosis and treatment of these problems. 

Note: Software Technology, Inc. no longer supports Windows 95 since Microsoft has discontinued support of this operating system. However, references to Windows 95 have been retained in the article for historical purposes.

Problems with Network Software

The following is a list of some of the issues that are discussed in this article:

• When lockup or corruption problems occur, it is important to verify that the most current server software, operating system software and network card drivers are installed. Although this is an easy concept in theory, in practice, it may not be so easy. This article will provide the necessary procedures and details for individuals who may not have the prerequisite background or experience in network administration.
• When using multi-user database software such as our software on networks, users on Windows Me/98/95 may experience data file corruption due to problems in Microsoft's Windows Me/98/95 network redirectors (VREDIR.VXD and NWREDIR.VXD), and Novell's redirector for Windows 95/98/NT.
• Users with Windows 2003/XP/2000/NT file servers may also experience intermittent lockups and possible data file corruption due to problems with Windows NT's opportunistic locking feature.
• Data corruption can occur on Novell platforms when some settings are optimized for performance because of a trade-off with reliability (i.e., TURBO FAT and opportunistic locking).

What is a Redirector?

The software that allows workstations or "clients" to "talk to" a server via a network is referred to as redirector software. Redirector software for networks is provided primarily by Microsoft and Novell. This software is an extremely critical component of any network. Each workstation on a network has its own redirector software. For example, if you have one workstation running Windows 98 and another workstation running Windows XP, each of these workstations has different redirector software. If there are "bugs" or "glitches" in the redirector software, it can cause all kinds of problems with other software programs.

Symptoms

We have had reports of problems with errors such as 1400-0-160-0 and 1400-0-69-0. Duplicate Key errors have been reported by our Data File Integrity Check (error 69) and Reindex Files programs. Other users have received intermittent lockups due to "Invalid Page Fault" errors.

Cause

Redirectors attempt to increase performance by caching parts of files in the memory of the local computer instead of getting the latest information from the network server. Unfortunately, the caching algorithms used have some problems that interfere with multi-user database programs such as Tabs3. Microsoft and Novell have been working on their redirector programs to reduce the data corruption problems.

It is important to note that these data corruption problems are due to problems in Microsoft and Novell software components. They are not due to Tabs3 or PracticeMaster programs. Although the file access routines used in Tabs3 Version 9 or later expose these problems more so than previous versions, it is important to note that the corruption problems are not limited to our programs.

Examples of other software companies reporting corruption problems with these redirectors are:

• Microsoft maintains a Knowledge Base that has articles documenting problems with the Windows 95 redirectors. This Knowledge Base can be found on the Internet at support.Microsoft.com:
  148367 - Possible Network File Damage with Redirector Caching
  174371 - Possible Database File Damage When Data Is Appended
  151912 - NWRedir Returns Cached File Size Information
  153470 - Incorrect Error Code Returned for Locked Files
• Data Access Corp (DataFlex 4GL) has a white paper on the Microsoft networking situation at: http://www.dataaccess.com/whitepapers/opportunlockingreadcaching.html
• Novell Knowledge Base (support.novell.com) article #2934705 reports problems with Client 32 and Delta Accounting Software, SAS Software and an SQL database.
• Novell Knowledge Base article #2913761 reports problems with GroupWise and MS client for NetWare Networks (nwredir.vxd).
• ADDSUM BUSINESS SOFTWARE, INC (accounting software vendor) reports problems with MS redirectors in a support memo located at: http://www.addsuminc.com/ad090998.htm
• PowerFlex Corp reports problems with Windows 95 and data integrity in an article at: http://www.pfxcorp.com/faq/multi.html.
• Corel Paradox (formally Borland/Inprise) Technical Information Document #20205 reports index problems with Paradox data files and vredir.vxd.

Solution

The solution to network or data corruption problems is a multi-pronged approach consisting of the following:

• Making sure all of your network servers AND clients have the most current Service Pack(s) installed. Failure to keep abreast of the most current patches available for your network can result in unnecessary problems and expense. It has been established unequivocally that data corruption will occur if Windows 95 workstations do not have the most current redirector software installed.
• Implementing the specified registry settings in this document for all workstations on the network. Registry settings can be implemented manually or by using our REDRTEST.EXE utility program.
• Disabling certain performance optimization features that affect reliability. Specifically, this includes:
• Disable Opportunistic Locking on any Windows 2003/XP/2000/NT servers.
• Disable Opportunistic Locking on any Novell servers.
• Disable TURBO FAT on any Novell servers.
• Making sure the most current drivers for your Network Interface Card have been installed.

CAUTION: Editing the Windows registry is typically not recommended because of potential problems that can occur when not done properly. We are not responsible for edits made to the registry. The recommended registry changes actually require the addition of values to subkeys and should not be attempted unless familiar with the registry. Any registry changes should be made by your network administrator or a qualified professional. Because of this recommendation, we have provided the recommended registry changes; however, we have not included step-by-step directions for implementing these changes. (Our Support personnel do not have the necessary training to help you with Windows registry changes.)

WARNING: The following disclaimer is used by Microsoft regarding editing of the registry: "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."

IMPORTANT: Microsoft recommends making a back up copy of the registry files before editing the registry. Refer to Microsoft documentation for details on how to back up the registry.

REDRTEST.EXE Utility Program

We have written a utility program called REDRTEST.EXE that can be used to test for current network redirector software on network workstations and most file servers. This program also tests for our recommended Windows registry settings including Windows 2003/XP/2000/NT opportunistic locking settings and can be used to automatically implement those registry settings if they need to be changed (provided you have sufficient rights and are logged in as an administrator).

The REDRTEST.EXE program file is installed when the System Configuration program is installed from the program CD-ROM. However, you want to make sure you have the most current version of the REDRTEST.EXE utility program. If the REDRTEST.EXE file installed from the CD-ROM has a date earlier than April 2003, you will want to download the most current version from the Internet.

The REDRTEST.EXE program file can be found on the Internet at:

           http://www.Tabs3.com/Support/Utilities.html

Redirector Identification

A redirector is the part of the operating system that lets a computer talk to another computer. The other computer may be a Novell server or other Windows computer. There are several redirectors available for Windows Me/98/95:

• Client for Microsoft Networks 
  Provided by Microsoft
  Used when connecting a Win Me/98/95 computer to a Windows computer.
• Client for NetWare Networks 
  Provided by Microsoft
  Used when connecting a Win Me/98/95 computer to a NetWare server computer.
• Client 32 Redirector
  Provided by Novell
  Used when connecting a Win Me/98/95 or a Win XP/2000/NT computer to a NetWare server computer.

A computer can have redirectors for both Microsoft and Novell servers loaded simultaneously. So a user could have:

Client for Microsoft Networks and
Client for NetWare Networks
          or
Client for Microsoft Networks and 
Client 32 Redirector
          but not
Client 32 Redirector and 
Client for NetWare Networks (since both are for NetWare).

Do I need to update redirectors for Windows 95 clients?

Any Windows 95 computer that is not using the most current redirector software MUST be updated. This applies to both Windows and Novell networks.

Do I need to update redirectors for Windows XP/2000/NT clients?

Redirectors are updated differently for Windows XP/2000/NT clients. Instead of downloading and updating separate patches (as is the method with Windows 98/95), patches are included in a consolidated Service Pack. Therefore, for Windows XP/2000/NT clients, simply verify that the most current Service Pack has been installed. The most current Service Packs for Windows XP/2000/NT clients are the same as those listed in the Microsoft Server section of this document. 

Do I need to update redirectors for Windows Me/98 clients?

If you are running under Novell Client 32, you need to make sure the most current version of Client 32 is installed for each workstation.

Do I need to implement registry settings for Windows Me/98/95 workstations?

Yes. Our REDRTEST.EXE utility program can easily do this for you.

Do I need to implement registry settings for Windows XP/2000/NT workstations?

Yes. Our REDRTEST.EXE utility program can easily do this for you.

How do you tell what redirector(s) a Windows Me/98/95 computer is using?

From the Control Panel, double-click Network to see which of the following network components is installed:

• Client for Microsoft Networks = VREDIR.VXD
• Client for NetWare Networks = NWREDIR.VXD
• Novell NetWare Client = CLIENT32.NLM

How can you tell which version of VREDIR.VXD or NWREDIR.VXD is being used on a Windows Me/98/95 computer?

1. Open Windows Explorer.
2. Navigate to your Windows folder.
3. Double-click the System folder.
4. Right-click VREDIR.VXD (or NWREDIR.VXD).
5. Click Properties.
6. Click the Version tab. The File Version will be shown on this tab.
   

          --- OR ---

1. Open Tabs3 for Windows Version 9 or later.
2. On the Help menu, click About Tabs3.
3. Scroll down in the lowest pane until you see Screen Resolution.
4. Directly underneath Screen Resolution, the MS Redirector Version and/or NetWare Redirector Version will be shown.
   

Note: Keep in mind that just because the file is shown in Explorer or the About Tabs3 dialog box doesn't indicate that the file is actually being used. The Control Panel | Network indicates which redirector(s) are being used.

How can you tell which version of the Client 32 Redirector is being used?

There are several methods that can be used.

1. Right-click the "N" icon in the System Tray. (If using Windows XP, it is possible that this icon could be hidden. One way to show the icon is to click the circle icon with the arrow pointing to the left; this will expand the system tray icons to show hidden icons.)
2. Select Novell Client Properties.
3. On the Client tab, the Client Version and Service Pack that is installed will be displayed. If no version number is shown, the redirector being used is older than version 3.0.

          --- OR ---

If you are using Windows Me/98/95:

1. From the Control Panel, double-click Network.
2. Click Novell NetWare Client (or Client for Netware Networks).
3. Click Properties.
4. Click the Client tab.
5. Under the First Network Drive, the version number will be shown. This information is shown only for the more recent redirectors. If no version number is shown, the redirector being used is older than version 3.0.
   

          --- OR ---

If you are using Windows NT:

1. From the Control Panel, double-click Network.
2. Click the Services tab.
3. Click Novell Client for Windows NT.
4. Click Properties.
5. Click the Client tab.
6. On the Client tab, the Client Version and Support Pack that is installed will be displayed. If no version number is shown, the redirector being used is older than version 3.0.

Note:  Windows XP/NT also shows the client version in the title bar of the initial Login window.

          --- OR ---

If you are using Windows XP/2000:

1. From the Control Panel, double-click Network Connections
2. Right-click Local Area Connection and choose Properties.
3. Click Novell NetWare Client or Novell Client for Windows.
4. Click Properties.
5. Click the Client tab.
6. Next to the Client Version line, the version number will be shown, along with any Service Packs installed (indicated by an SP#). This information is shown only for the more recent redirectors. If no version number is shown, the redirector being used is older than version 3.0.

Recommended Registry Settings and How to Download Current Redirectors

The following information includes technical information, recommended registry settings and how you can download the most current redirector from the Internet.

SERVER ISSUES 

It is important to make sure that the server being used has the latest Service Pack installed. The following lists the most current Service Packs for both Microsoft and Novell servers and also identifies issues known to cause data corruption.

Microsoft 2003/XP/2000/NT Servers 

Make sure that the latest Service Pack is installed. As of this writing (February 2007), the latest versions of Windows servers are:

To determine which Service Pack is installed on a Microsoft server:

• Right-click My Computer and select Properties. The Windows operating system, version and service pack will be shown.

Problems with Opportunistic Locking on 2003/XP/2000/NT Servers

Users can also experience file corruption due to the use of opportunistic locking by Windows NT. This is a problem that affects networks with Windows 2003/XP/2000/NT servers. Novell networks are not affected.

What is opportunistic locking?

Opportunistic Locking is another attempt at allowing computers on a network to cache data locally instead of retrieving data from the Windows 2003/XP/2000/NT server with the hope of improving performance. Again, there seems to be problems in at least some situations where opportunistic locking doesn't work quite right.

Opportunistic locking is explained in Microsoft Knowledge Base Article #129202, "Explanation of Opportunistic Locking on Windows NT". It is interesting to note that this article states:

"Oplocks are a significant performance enhancement, but have the potential to cause lost cached data on some networks ..."

Microsoft has acknowledged problems with Opportunistic Locking in Microsoft Knowledge Base Article #303528, "How to Keep a Jet 4.0 Database in Top Working Condition".

How is opportunistic locking disabled?

We recommend disabling opportunistic locking at the Windows 2003/XP/2000/NT Server in order to prevent data corruption. To do so, you can use our REDRTEST.EXE utility program on a Windows 2003/XP/2000/NT Server or you can edit the Registry (on the 2003/XP/2000/NT server).

HKEY_LOCAL_MACHINE/System/CurrentControlSet/Services/LanmanServer/Parameters
          EnableOpLocks = 0 (hex)
          EnableOpLockForceClose = 1 (hex)
          CachedOpenLimit = 0 (hex)

Note: The above values should be added as DWORD values if not present.

Novell NetWare Servers

Make sure that the latest Support Pack (SP) is installed. As of this writing (February 2007), the latest versions of NetWare servers are:

To determine which Support Pack is installed on a Novell server:

• From the System Console command prompt, type Version. The NetWare Server version and Support Pack will be shown.

Problems with TURBO FAT Causing Data Corruption on Novell NetWare Servers 

NSS Note: The following TURBO FAT issue does not apply to NetWare volumes that use an NSS filesystem. This issue only affects unpatched servers that use the old FAT file system. If you use an older Novell NetWare file server, you can download the patch as discussed in the following, or consider migrating the filesystem to NSS.

By default, older Novell servers used a special File Allocation Table feature called TURBO FAT to improve performance. However, there have been data corruption problems (not related to our software) reported with this feature. The corruption occurs while the file is in the server's memory. When the file is modified by an application and rewritten to the server's hard disk, the corruption is introduced. Novell's Technical Information Document 10064734, "How to Disable TurboFat", reports that "The problem is typically seen on NetWare 4.10, 4.11, 5.0, 5.1 and 6.0 file servers with database applications which use large files."  The definition of a "large file" is somewhat subjective because it depends on how the hard drive was formatted and the file block size. 

The aforementioned Novell article includes instructions to download a Novell patch that will disable this feature. The patch includes files named TURBODIS.NLM and TDIS600.NLM that when installed will disable the TURBO FAT feature. 

Because many data files in our software can be considered large, such as the client file, the archive files, the fee and cost transaction files, etc., we STRONGLY recommend downloading this Novell patch and disabling this feature. Alternatively, consider migrating to an NSS filesystem.

Additional details regarding TURBO FAT can be found in the following Novell Technical Information Documents (TIDs) at support.novell.com: 

• 2960009 - TURBODIS.NLM to prevent database corruption
• 10064734 - How to Disable NetWare Turbo Fat
• 10050033 - BTRIEVE application report STATUS 2 error
• 10062567 - Effects of applying TURBODIS.NLM
• 2947821 - CC:Mail Database Corruption
• 10012238 - Database Rebuilds occurring on a nightly basis
• 10064679 - Does Turbofat cause corruption of GroupWise databases?
• 10051136 - E811 errors occur often in post office and on client
• 10052321 - TurboFat on NetWare 5 and cc:Mail Database Corruption

Problems with Opportunistic Locking on Novell NetWare Servers 

Novell NetWare also includes an Opportunistic Locking feature. We recommend that Opportunistic Locking be DISABLED at the Novell NetWare File Server. This applies to servers running under Version 5.0 SP5, Version 5.1 SP2, or later.

This setting can be disabled by:

• editing the AUTOEXEC.NCF file (system directory) or the STARTUP.NCF file (DOS partition); or 
• typing the command at the command line of the File Server. 

The command to disable the setting is the same regardless of which method is used to implement it. The command is:

SET CLIENT FILE CACHING ENABLED = OFF

We recommend editing the AUTOEXEC.NCF file, which requires rebooting the server after adding the command. However, the command line method can be used temporarily until it is more convenient to reboot the server.

Network Interface Card Issues

Network Interface Card Drivers

Always make sure the latest Network Interface Card (NIC) driver is being used. Current drivers are typically available from the manufacturer of your NIC card.

The Realtek NIC drivers that Microsoft placed on the Windows 98 CD-ROM are problematic and definitely cause data corruption. If you are using these drivers, you need to get the latest drivers from Realtek or use a different NIC. (Details can be found in Microsoft's Knowledge Base Article 189778, "Possible Problems with Windows 98 Realtek Network Adapter Drive" on the Internet at support.Microsoft.com.)

Power Management

NICs can be configured with their own set of power management features, but it may be necessary to disable these features. Enabling power management on a NIC can cause connection issues, resulting in fatal errors within the software. More information is available in KB Article R10339, "Power Management Issues with Tabs3 and PracticeMaster Software Products."

Speed and Duplex Configurations  

Improper configuration of NIC link speeds and duplex settings can cause sluggish network performance, timeout errors and lost network connections, all of which can in turn lead to data corruption. It is important that each NIC, including those on the file server(s), are configured to match the speed and duplex settings used by the ports on the hubs or switches to which they are connected.

Many NICs, hubs and switches support auto-detection (also called auto-sensing and auto-negotiation), which automatically detects and matches the speed and duplex settings configured for the connected hub or switch port. However, auto-detection may not work correctly when connecting certain brands of NICs, hubs and switches to certain other brands. Therefore, it may be necessary to manually configure the NIC to match the exact speed and duplex settings used by the hub or switch port. The following articles from Microsoft's Knowledge Base and Novell's Knowledge Base provide detailed information regarding speed and duplex settings:

• Microsoft Article 325487 - How to Troubleshoot Network Connectivity Problems
• Microsoft Article 247609 - Poor Performance with Catalyst 2948G LAN Switch
• Novell Article 10023448 - Should I Use Half Duplex or Full Duplex?
• Novell Article 10018424 - Server Will Close All Communication
• Novell Article 10016506 - TCPIP Significantly Slower than IPX

References  

• Microsoft Article 325487 - How to Troubleshoot Network Connectivity Problems
• Microsoft Article 247609 - Poor Performance with Catalyst 2948G LAN Switch
• Novell Article 10023448 - Should I Use Half Duplex or Full Duplex?
• Novell Article 10018424 - Server Will Close All Communication
• Novell Article 10016506 - TCPIP Significantly Slower than IPX
• KB Article R10790 - Outdated Redirector Message When Starting Our Software
• KB Article R10700 - Troubleshooting Worksheet
• KB Article R10104 - REDRTEST.EXE Utility Program
• KB Article R10054 - TESTIO.EXE - Testing for Basic Network Reliability
• KB Article R10011 - Troubleshooting Invalid Page Fault and Other Exception Errors

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