MATLAB Answers

1

Why do I receive warnings regarding non-responsive Change Notification Handles?

When I change my current working directory or add a directory to the MATLAB path using the ADDPATH command, I often see the warning:
Warning: Change notification handle for remote <directory name> is not responsive.
This server does not appear to support UNIX-style directory timestamp updates.
Network latency may be causing delayed arrival of change notifications.
Type 'help changeNotification' for more info.

1 Answer

Answer by MathWorks Support Team on 1 Jun 2017
 Accepted Answer

MATLAB uses a Microsoft feature called Change Notification Handles (CNHs) to track if a file has been updated in a directory which has been added to the MATLAB path or is the current directory.
This warning may occur if MATLAB does not receive the change notification handle in a timely manner due to network or fileserver latency which delays the arrival of the change notification handle. For example, this may occur on NetApp filers, because NetApp filers are slower to issue the change notification handles (CNH) than the Windows servers.
Because many years ago there were problems with systems that would support change notification handles but not implement the corresponding behavior, the MATLAB code makes an assumption on how quickly the CNH is in a signaled state before it is interpreted as non-responsive.
These warnings regarding unresponsive change notification handles are likely benign, because the CNHs do arrive after a small delay and MATLAB is able to use them to detect changes in directories.
To disable these warning messages, execute:
 
system_dependent('DirChangeHandleWarn', 'never')
To learn more about the MATLAB function SYSTEM_DEPENDENT and options for using CNH's, review the "Change Notification" documentation by typing:
 
doc changeNotification
doc changeNotificationAdvanced
A much more serious issue occurs when Windows exhausts its supply of change notification handles. Unfortunately, disabling the unresponsive change notification handle warning will also disable the warning regarding exhausted change notification handles. Please see the related solution 1-18IFI, 'Why do I receive a warning regarding exhausted change notification handles?' for more information on this issue.

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