Memory leaks, regardless of where they occur, tend to
manifest the same behavior. As a process continues to run, a decreasing amount
of memory is available over time and eventually the process can run out of
memory to allocate.
Internet Information Server (IIS) has no known
memory leaks at this time. There are, however, typically dozens of components
that are used within the Inetinfo process that may have memory leaks. Over
time, these leaks can accrue, potentially causing the entire process to stop
Be aware that on high volume sites, a growth in memory
over the first 24 hours of use is not uncommon. IIS caches much of its data and
the Time To Live (TTL) on the cache is 24 hours. In fact, the IIS file cache is
set to use up to half of available memory by default. IMPORTANT
: This article contains information about modifying the registry.
Before you modify the registry, make sure to back it up and make sure that you
understand how to restore the registry if a problem occurs. For information
about how to back up, restore, and edit the registry, click the following
article number to view the article in the Microsoft Knowledge Base:
Description of the Microsoft Windows Registry
: You can use the procedures given below to examine any process
that you suspect has a memory leak; to do so, replace "Inetinfo.exe" with the
name of your process.
To get memory usage logs of the Inetinfo
process which can be resolved against modules that are allocating memory,
complete the following steps:
- Install the necessary symbol files.
- At the command prompt, type the
- To enable memory allocation tracking:
- Start Registry Editor (Regedt32.exe).
- Locate the GlobalFlag value under the following key in
- On the Edit menu, click DWORD, type 23000, and then click OK.
- Quit Registry Editor.
- Download two utility programs, Dh.exe (Display Heap) and
Dhcmp.exe (Heap Compare), into a temporary directory. Both programs are
available at the following Web site:
Dh.exe is included as part of the Windows NT 4.0 Resource Kit, Supplement 2 or
higher. To download it, expand Network/Server Administration Tools from the tree on the left, and click Dh.exe.
is included as part of the Windows NT 4.0 Resource Kit, Supplement 4. To
download it, expand New Tools from the tree on the left, and click New Tools with Supplement Four.
- Restart your web server.
- Press CTRL+ALT+DELETE, click Task Manager, click the Processes tab, and locate the process ID (PID) for Inetinfo.exe.
- Open a command window, switch to the directory into which
you copied Dh.exe and Dhcmp.exe, and enter the following
dh -p PID -f before.txt
- Wait for the leak to show, and then enter the following
dh -p PID -f after.txt
- Once the logs are captured, enter the following
dhcmp -d before.txt
- Send the Before.txt, After.txt, and Cmp.txt files to your
Microsoft Support Professional via FTP. (If you like, you may zip these files.)
Please see the Microsoft File Exchange Web page for information on transferring
files via FTP:
- Send email to your Microsoft Support Professional with the
- The version of Windows NT and Service Pack that you are
- Any IIS hotfixes that you have installed.
- A full description of the events leading up to the
system not responding.
- A full description of your web site's
For detailed instructions on how to use the Dh.exe utility,
please click the article number below to view the article in the Microsoft
How to Use Dh.exe to Troubleshoot User-Mode Memory Leaks
For additional information, including the
command-line options of Dh.exe, see the following article:
How to Use Display Heap (DH.EXE) Resource Kit Utility
Article ID: 253706 - Last Review: January 10, 2015 - Revision: 3.0
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