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Q134367: PRB: "Too Many Files" Open in FoxPro for Macintosh

Article: Q134367
Product(s): Microsoft FoxPro
Version(s): MACINTOSH:2.5x,2.6a,3.0b
Operating System(s): 
Keyword(s): kbenv
Last Modified: 15-FEB-2000

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The information in this article applies to:

- Microsoft FoxPro for Macintosh, versions 2.5x, 2.6a 
- Microsoft Visual FoxPro for Macintosh, version 3.0b 
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SYMPTOMS
========

When several users are running a FoxPro for Macintosh application and using
tables stored on a server, it is possible to receive the message:

  Too many files open

CAUSE
=====

This indicates that there are not enough file handles on the server for the
number of users and files that are open. This usually happens when the server is
another Macintosh connected to through the AppleTalk services provided with the
System Software. The absolute limit of file handles on a Macintosh is 342. Note
that each user that opens a file on a server uses another file handle.

WORKAROUND
==========

The following are suggestions that may help reduce the number of file handles
being used on the server:

1. Place the application the local hard drive (on each workstation).

2. Use the TMPFILES setting in the CONFIG.FPM file to make sure that temporary
  files are going to the local hard drive (of each workstation).

3. Change the application so that tables and other files are only open as long
  as they are needed, instead of keeping them open throughout the application.

Another option is to upgrade to a server operating system that will support a
higher limit of open files, such as AppleShare Pro, Novell Netware, or Microsoft
Windows NT.

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

The following information was provided by Apple Developer Support on the maximum
number of File Control Blocks (FCBs) available in the Macintosh Operating System
File Manager, and therefore, the number of files that can be open at one time.
This information only applies to System 7.x.

"While System 7 increases the number of FCBs as required, there is an absolute
limit imposed by the File Manager. This limit is 342 FCBs and is documented in
Inside Macintosh, File p. 2-81:

'The initial size of the FCB buffer is determined by the system startup
information stored on a volume. Beginning in system software version 7.0, the
File Manager attempts to resize the FCB buffer whenever the existing buffer is
filled.

You can find the (http://support.microsoft.com/download/support/mslfiles/the)
beginning of any particular FCB by adding the size of all preceding FCBs to the
size of the FCB buffer length word (that is, 2). This offset from the head of
the FCB buffer is used as the file reference number of the corresponding open
file. Because the current size of an FCB is 94 bytes, the first few valid file
reference numbers are 2, 96, 190, 284, 378, 472, and so on. The maximum size of
an expandable FCB buffer is 32,535 bytes, so there is an absolute limit of 342
FCBs in the FCB buffer.' "

Additional query words: 3.00b VFoxMac 2.50b 2.50c FoxMac

======================================================================
Keywords          : kbenv 
Technology        : kbHWMAC kbOSMAC kbVFPsearch kbAudDeveloper kbFoxproSearch kbFoxPro260aMac kbVFP300bMac
Version           : MACINTOSH:2.5x,2.6a,3.0b

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