Windows NT File Sharing Problems

Kenn's
Tech
Notes

19980601: Windows NT File Sharing Problems

June/1998
Tech Note #1

Tip of the Month! This month's best tip comes from Patrick L, who shared information pertaining to the way Microsoft Windows NT caches the file handles (RFCBs) associated with files it has opened on behalf of a client request. The process is called "opportunistic locking", and although it is designed to improve performance, Microsoft admits that it "may fail to work correctly depending on how the file has been opened by the application". It has certainly caused problems in the division, notably the now-famed "Magnificent Seven" problem, in which a lab full of workstations attempting to access a network resource simultaneously would see about seven (the actual number varied) connect normally, while the rest would appear to hang. After about a minute, the remaining "hung" workstations would suddenly open the resource at precisely the same instant.

If you wish disable opportunistic locking, you need to create (or change) two DWORD entries in the registry of your NT server.

Under
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters
create or change the EnableOplocks parameter to 0 (false).

Under
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters
create or change the CachedOpenLimit parameter to 0.

For those of you who feel uncomfortable editing the registry (this is a healthy feeling, by the way), an automated procedure will be developed so that the team leaders running the summer ('98) computer preventative maintenance program can perform this modification easily.

For more information see Microsoft Technical Articles:
Q134637, Q124916, and Q126026.

DISCLAIMER: This document is intended for the reference of computer support personnel within Winnipeg School Division No. 1. There is no warranty or liability if procedures recommended here have an adverse affect on any systems. Use them at your own risk. Any trademarks mentioned are the property of their owners, none of whom have certified any information provided here. Opinions expressed here are personal only and do not represent the policy of Winnipeg School Division No. 1 or any other organization anywhere.

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