MS Access Crashes on TreeView.Nodes.Clear

I found a specific situation where MS Access always crashes to desktop.  Here are the ingredients:

  1. A bound Form with a Microsoft TreeView Control, version 6.0.
  2. Form’s “Allow Additions” property set to “No”
  3. TreeView populated using the Form_Current() event.
  4. Prior to populating the TreeView, calling .Nodes.Clear on the TreeView object.
  5. To set up the crash, filter the form to an empty recordset.
  6. Click on the Home ribbon and the Toggle Filter button.

Download Testcase File: treeview-testcase.accdb

Workaround

In the Form_Current() event, add a DoEvents command immediately before Nodes.Clear.

Set MyTree = Me.TreeView0.Object
DoEvents
MyTree.Nodes.Clear

InStr Performance for VBA

I solved a mysterious bottleneck last night while working with large string values in MS Access. My VBA code was reading a file to a string variable, checking several values near the beginning of the string, and then manipulating and saving the string to the database.

Oddly, one of the slowest parts of my code was the several InStr calls that were only checking the first few hundred bytes of the string. I could alleviate part of the problem by copying the beginning of my file to a shorter string value, but in so doing I also noticed unexpected results from the InStr return value.

Continue reading InStr Performance for VBA

Forcing PHP to Sort Like MySQL

If you ever have to do a case-insensitive array sort in PHP, you will eventually notice that the results don’t match the MySQL latin1_swedish_ci collation. They just aren’t the same. The difference comes from a set of six characters that fall between the upper-case and lower-case alpha characters of ISO-8859-1.

Specifically, [ \ ] ^ _ ` are the troublemakers. A simple example would involve sorting the phrases “Hello” and “[Hello]”. In MySQL, “Hello” comes first. In PHP, “Hello” comes last.

If this is driving you crazy, all you will need to do is trick PHP into using an upper-case sort instead of a lower-case sort.

$strings = ['hello', '[Hello]', 'Hello'];
usort( $strings, 'mysql_simulator' );
var_dump( $strings );

function mysql_simulator( $a, $b ) {
return strcmp( strtoupper( $a ), strtoupper( $b ) );
}

I hope this will save you some of the research in solving that pesky little difference.

Cannot Use Dynamic Class Name

It seems I’ve discovered a new kind of PHP error that isn’t documented anywhere on the web yet. Here is a simple example and explanation to help correct your code.

class MyClass {}
$obj = new MyClass;
$test1 = MyClass::class;    // Right
$test2 = get_class( $obj ); // Right
$test3 = $obj::class;       // Wrong

That last line in my code sample produces the following error in PHP 7.4.

Fatal error: Cannot use ::class with dynamic class name in […][…] on line 5

This is the PHP way of saying that you have to switch to the get_class() function when retrieving the fully qualified class name of an object.

Note: An existing RFC proposes to change this behavior in PHP 8, so this particular error message might not exist in some future versions.

Server Crippled by Updates Again

February update cycle again sent my server into a reboot loop, shutting down all services until I could diagnose the problem on site.

Following the same steps as in my previous post, I switched the boot choice to Safe Mode, and observed another boot failure. This time instead of getting into the weeds of troubleshooting the update system with a second Safe Mode boot, I decided to let the server go back to the normal boot mode, because some other websites have reported this as a good solution.

In this case, the failed Safe Mode boot followed by no other action did successfully restore the server.

After reviewing the Event Viewer logs, I could only find a repeated Event ID 1074, “TrustedInstaller.exe has initiated the restart”. KB2992611 and KB890830 both installed successfully before the loop, then KB4502496, KB2822241, and KB4537814 installed after the loop.

My current recommendation is to disable automatic updates for Windows servers and only perform update checks while on site. Also, run the update check twice in a row. The servicing stack update from December didn’t show up until after recovering from the reboot loop and then checking again for more updates.

Reboot Loop After KB4525246 Update

Several other sites confirmed recent server failures after running Windows Updates. Here are the basic steps I used to recover.

Attach a keyboard and enter BIOS setup. Make sure Quick Boot is disabled.

Press F8 while restarting the server to open the Advanced Boot Options menu.

I tried Safe Mode, but did not see a successful boot there.

Next I tried Repair Your Computer, which brought me to the “Choose an option” screen.

Select Troubleshoot, then select Command Prompt. Follow the instructions to log in as one of the administrators.

Continue reading Reboot Loop After KB4525246 Update

Solving Disconnected Folders Over Wi-Fi

Avoid the First Default Setting for Share Caching

I’m starting to realize that the Offline Files feature in Windows causes more problems than it solves when it comes to unreliable network connections.

In 2016, I described how to minimize the effects of an occasionally high ping when the slow-link mode goes into effect: Offline Files Stay Disconnected

But that doesn’t solve the problem.  Fine-tuning or even disabling the slow-link mode forces the Client Side Cache (CSC) to use its “Action on server disconnect” configuration any time the network isn’t performing perfectly.  The default behavior, “Work offline”, treats each affected (meaning cache-enabled) share as being totally unavailable and then the CSC attempts to retrieve cached copies.  This happens even if the server is still available but failed a single ping check.

Why is this still a problem?  Well, in practice, most files don’t need to be available offline.  By default, the Windows file server is configured, and the Windows client is designed to allow each user to select individual files as “Always available offline” from the file context menu.  When a user selects this option, that one file is copied to the CSC, and in theory that one file is always available.  This allows for targeted use and minimal sync time.  The problem arises with all the other files.  When the CSC goes offline and marks the shared folder as disconnected, it effectively blocks access to all the files that were never cached, even if the server and its files are still available.

At this point, you and I now understand the situation that needs to be avoided.  We don’t want to have a large number of files under the unnecessary clutches of the CSC, regardless of network quality.

Update 08/17/2018

At first, I thought the solution was to change the file server’s default configuration of allowing users to decide which files are cached.  I changed folders that needed maximum online availability to be set to “No files or programs from the shared folder are available offline.”  This server setting automatically disables the CSC.

Unfortunately, the result was that the folders configured for offline caching worked great, but the folders configured for no offline caching only worked until some network error or server reboot.  In this configuration, once a path became disconnected, an Offline Files message is logged in the Event Viewer, and even though no files are being cached the entire path becomes unavailable.  At that point, the workstation persistently throws Error 0x80070035 any time that particular path is accessed, until the workstation is rebooted.

The only solution I’ve found that works now is to completely disable the Offline Files feature on the workstation.  With Offline Files disabled from the Control Panel, the network and server errors are now transient and I am not having any problems with disconnected paths or persistent errors.

Offline Files is ultimately broken and does not improve the Windows experience.

Windows 2012 Can’t Ping NVR Host

I just resolved a long-term problem where one specific Windows 2012 server was unable to ping one specific device on the same LAN.

There were no relevant resources or similar-looking cases on the web.  Everything else on this LAN worked normally.  The server could ping all other clients, and the clients could ping the server and the NVR.  I just could not get the server to ping the NVR for the life of me.

I suspected at one point that this was a routing issue due to my desire for strong security policies around IOT devices.  This turned out not to be the case as I could find nothing wrong with the router or any routing tables.

At last, I decided this problem was so specific that it could be a bug in the NVR itself.  In this case, the only thing special about the Windows server from the NVR’s perspective was that the server was providing both DHCP and DNS to the NVR.  I tried disabling each service, and found exactly what I was looking for.

The NVR will not respond to pings from its DNS server.

I don’t know why this is broken and don’t really care to investigate any further.  The workarounds are either:

  • Create a DHCP reservation with its own option to specify a 3rd-party DNS server, OR
  • Disable the NVR’s DHCP client and set a static address with an alternative DNS server address value.

In my case, the NVR does not need to use the local DNS server, so this is an easy fix.  So long as my server’s IP address is not used in the NVR DNS configuration, everything works normally and the server can ping the NVR.

High Resource Use by Start Screen

While diagnosing what I thought was a Windows Update failure, I discovered unrelated massive resource consumption and file scanning activity apparently tied to the Start screen in Windows 2012.

Symptoms:

10 to 20% constant CPU usage by Windows Explorer.

Rapid file scanning or Shared Folder usage in the case of folder redirection.

Triggers:

Resource consumption begins immediately after opening the Start screen and performing a keyboard search.

Closing the Start screen does not help.

Workarounds:

Sign out the current user.  This action will shut down Windows Explorer, preventing the unwanted symptoms until triggered again by a user.

Android Studio Setup Error

While installing Android Studio for the first time, I encountered the message below.

The following SDK component was not installed: Google Repository

Simply clicking the “Retry” button allowed the installation to continue successfully.

Relevant log dump quoted below.

java.nio.file.AccessDeniedException: C:\Users\{user}\AppData\Local\Android\Sdk\extras\google\m2repository.backup\com\google\android\support\wearable\1.0.0\wearable-1.0.0-javadoc.jar -> C:\Users\{user}\AppData\Local\Android\Sdk\extras\google\m2repository\com\google\android\support\wearable\1.0.0\wearable-1.0.0-javadoc.jar
Warning: Failed to move original content of C:\Users\{user}\AppData\Local\Android\Sdk\extras\google\m2repository back into place! It should be available at C:\Users\{user}\AppData\Local\Android\Sdk\extras\google\m2repository.backup
java.io.IOException: Failed to move away or delete existing target file: C:\Users\{user}\AppData\Local\Android\Sdk\extras\google\m2repository
Move it away manually and try again.
Warning: An error occurred during installation: Failed to move away or delete existing target file: C:\Users\{user}\AppData\Local\Android\Sdk\extras\google\m2repository
Move it away manually and try again..
Warning: Observed package id 'extras;google;m2repository' in inconsistent location 'C:\Users\{user}\AppData\Local\Android\Sdk\extras\google\m2repository.backup' (Expected 'C:\Users\{user}\AppData\Local\Android\Sdk\extras\google\m2repository')

Preparing "Install Google Repository (revision: 54)".
Found existing prepared package.
"Install Google Repository (revision: 54)" ready.
Finishing "Install Google Repository (revision: 54)"
Installing Google Repository in C:\Users\{user}\AppData\Local\Android\Sdk\extras\google\m2repository
"Install Google Repository (revision: 54)" complete.
"Install Google Repository (revision: 54)" finished.