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Q259928: PRB: REPLACE Command Runs Slowly When Applied to a Remote Table

Article: Q259928
Product(s): Microsoft FoxPro
Version(s): WINDOWS:6.0
Operating System(s): 
Keyword(s): kbDatabase kbOSWinNT kbRegistry kbvfp600 KbDBFDBC kbGrpDSFox kbDSupport
Last Modified: 11-JUN-2002

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 6.0, on platform(s):
   - the operating system: Microsoft Windows NT 
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SYMPTOMS
========

If a REPLACE ALL statement (or a REPLACE statement that affects a very large
number of records in a table) is applied to a relatively large table that
resides on a remote computer and the network is Microsoft Windows NT-based and
uses the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol, the
statement may take a very long time to complete.

RESOLUTION
==========

Do not permit the redirector to use the cache manager to cache the contents of
files. This is accomplished by disabling the UtilizeNtCaching startup parameter
for the Workstation Service.

IMPORTANT: This article contains information about modifying the registry. Before
you modify the registry, make sure to back it up and make sure that you
understand how to restore the registry if a problem occurs. For information
about how to back up, restore, and edit the registry, click the following
article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

You can modify the startup parameters for the Workstation Service by using the
Registry Editor. Unless otherwise indicated, these value entries are located in
the following Registry path:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters

Move to this Registry path and add the following value if it is not already
there:

+--------------------------------+
| Value Name: | UtilizeNtCaching | 
+--------------------------------+
| Data Type:  | REG_DWORD        | 
+--------------------------------+
| Data:       | 0                | 
+--------------------------------+
| Radix:      | Hex              | 
+--------------------------------+

After making this change, you must restart the computer.

NOTE: Disabling Windows NT caching may result in a performance decrease with some
applications.

MORE INFORMATION
================

The REPLACE statement appears to execute at an acceptable rate for about the
first 25 percent of the records that are replaced. After that, however, no
replacements occur for a minute or more. From this point on, replacements occur
in spurts between long time delays until all of the replacements have
completed.

The UtilizeNtCaching parameter is enabled by default. This parameter indicates
whether the redirector uses the cache manager to cache the contents of files.
Disable this parameter only to guarantee that all data is flushed to the server
immediately after it is written by the application.

Steps to Reproduce Behavior
---------------------------

1. Create a table that is at least 350 MB in size and ensure that it resides on
  a remote PC that uses Windows NT 4.0.

2. From your local PC, execute a REPLACE ALL statement from the Visual FoxPro
  Command window. Make this statement replace one field with one value on the
  table that you created in step 1.

NOTE: You may be able to achieve further performance improvements by using the
SYS(3050) function. See the "References" section for articles providing more
information on this function.

REFERENCES
==========

For additional information on NT registry entries, click the article numbers
below to view the articles in the Microsoft Knowledge Base:

  Q102981 Workstation Service Entries

  Q163401 How to Disable Network Redirector File Caching

For additional information on the SYS(3050) function, click the article numbers
below to view the articles in the Microsoft Knowledge Base:

  Q176483 PRB: Large Amounts of RAM Seem to Process Data Slowly

  Q190312 PRB: 'Computer Not Responding' When Certain Commands Issued

  Q129311 Visual FoxPro Has 3 New SYS Functions Related to Memory

Additional query words:

======================================================================
Keywords          : kbDatabase kbOSWinNT kbRegistry kbvfp600 KbDBFDBC kbGrpDSFox kbDSupport 
Technology        : kbVFPsearch kbAudDeveloper
Version           : WINDOWS:6.0
Issue type        : kbprb

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