Internet Explorer 9 & Reliability: Understanding IE9 ‘Hang Resistance’ feature

Hangs‘ are the most common source of user disruption in applications. When an application hangs (or “freezes”), the entire user interface becomes unresponsive. Browser hangs are equally unpleasant. In earlier IE versions, when a tab hangs, you could not interact with the other open tabs or browser windows.

Internet Explorer 9 is integrated with a ‘Hang Resistance’ feature, which ensures when a site hangs in a tab in IE9, the rest of the browser remains unaffected.

Browser hangs will occur when the message queue becomes stuck. Example, a tab becomes unresponsive due to a plug-in, so the tab cannot process any messages designated for itself in the shared queue. This holds up the other messages in the queue, creating a traffic jam effect. As you persistent click around the browser, your actions generate messages that get queued up but won’t be processed since the hung tab still hasn’t processed the current message.

IE9 doesn’t allow this traffic jam to occur. The frame window periodically checks on the tabs to see if they’re hung. When the frame finds out that a tab is hung, it detaches the messages for that tab into a temporary location. This frees up the queue and the other tabs and the frame window can continue to process their messages while one of the tabs is still hung.

When a tab remains unresponsive for 8 seconds after the frame window detects it to be hung, it is likely permanently hung. In that case you may want to recover the contents of the hung tab. IE displays the hang recovery notification for that tab when you interact with the tab.

Clicking the “Recover Web page” button on the notification initiates tab recovery for the hung tab process and sends an error report for the hang in the process. The other tab processes remain unaffected.

The hung tab will send an error report for the hang with the following actions:
– Closing the tab
– Refreshing the tab
– Navigating to a different Web site on the tab
– Closing the IE window

IE9 also provides you with the ability to recover from hangs caused by the Web page, plug-ins, long running scripts or add-ons.

For a detailed read on how IE9 provides a hang-resistant user experience, visit the IEBlog.

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