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Exchange Server 2007 Transport: 452 4.3.1 Insufficient system resources
Posted by Bharat Suneja at 5:24 PM
In my hotel room in Orlando, getting ready for a presentation tomorrow morning at TechMentor. When trying to telnet to the SMTP port of an Exchange Server 2007 Hub Transport server, I got the following error:
The Application Event Log has Event ID 15002 from MSExchangeTransport saying "The resource pressure is constant at High. Statistics... ". The event goes on to tell you that inbound mail submission has stopped, and it's due to disk space being low on the volume where the queue database is located.
Figure 1: Event ID 15002 logged by MSExchangeTransport
Exchange Server 2007 transport queues are not the familiar .eml files you see in Exchange Server 2003/2000, which reside in the \mailroot\vsi <1>\queue folder (<1> is the instance number of the SMTP virtual server) on the file system. Queues have been moved to a JET database.
What's Back Pressure?
In Exchange Server 2007, the Transport service monitors system resources such as disk space and memory on Transport servers (the Hub Transport and the Edge Transport servers), and stops message submission if it is running low on these resources. It continues to deliver existing messages in the queue. When resource utilization returns to normal, it resumes message submission. The feature is called Back Pressure.
In this case, Exchange required 4 Gigs of free disk space on the volume where the Queue database was located - I had about 3.95 Gigs. :)
Many configuration options for transport servers are saved in an XML file named EdgeTransport.exe.config (same file name on both Edge and Hub Transport servers) located in \Exchange Server\Bin\. You can edit the file to disable Back Pressure, or modify the parameters to more accurately define what's high utilization for your deployment or server configurations, as explained in the above docs.
Another resolution, and the one I used in this case, was to move the Queue database to another volume with ample of free space, using the following procedure:
Related Posts:
- Exchange Server 2007: How to turn off the Back Pressure feature on transport servers
452 4.3.1 Insufficient system resources
Not a good thing the night before a presentation - Murphy's law at work again!The Application Event Log has Event ID 15002 from MSExchangeTransport saying "The resource pressure is constant at High. Statistics... ". The event goes on to tell you that inbound mail submission has stopped, and it's due to disk space being low on the volume where the queue database is located.
Figure 1: Event ID 15002 logged by MSExchangeTransport
Exchange Server 2007 transport queues are not the familiar .eml files you see in Exchange Server 2003/2000, which reside in the \mailroot\vsi <1>\queue folder (<1> is the instance number of the SMTP virtual server) on the file system. Queues have been moved to a JET database.
What's Back Pressure?
In Exchange Server 2007, the Transport service monitors system resources such as disk space and memory on Transport servers (the Hub Transport and the Edge Transport servers), and stops message submission if it is running low on these resources. It continues to deliver existing messages in the queue. When resource utilization returns to normal, it resumes message submission. The feature is called Back Pressure.
In this case, Exchange required 4 Gigs of free disk space on the volume where the Queue database was located - I had about 3.95 Gigs. :)
Changes to Back Pressure settings in Exchange Server 2007 SP1
The Back Pressure settings in Exchange Server 2007 RTM stop inbound mailflow if free disk space is below 4 Gigs. This static threshold has been lowered in SP1 to a more realistic 500 Mb.
Many configuration options for transport servers are saved in an XML file named EdgeTransport.exe.config (same file name on both Edge and Hub Transport servers) located in \Exchange Server\Bin\. You can edit the file to disable Back Pressure, or modify the parameters to more accurately define what's high utilization for your deployment or server configurations, as explained in the above docs.
Another resolution, and the one I used in this case, was to move the Queue database to another volume with ample of free space, using the following procedure:
- Add the following key in the <AppSettings> section in EdgeTransport.exe.config:
<add key="QueueDatabasePath" value="D:\Queue\QueueDB" />
This is documented in "How to Change the Location of the Queue Database" - Restart the MSExchangeTransport service, and message submission resumes.
Related Posts:
- Exchange Server 2007: How to turn off the Back Pressure feature on transport servers
Labels: Administration, Exchange Server 2007, SMTP
16 Comments:
Understanding Back Pressure
Thank you for your post. It helped me see why in my test virtual environment I couldn't send not even an e-mail (and was wonderring for some time now what I did wrong .. my VM had 10 Gig hard drive and it had only 3.9 Gig free :( )
So what is the unit for PercentageDatabaseDiskSpaceUsedHighThreshold? I set it to 1024000000 (1GB?) and restarted MSExchangeTransport and still got 15002 errors with mail stuck in the outbox. I finally just turned off backpressure altogether but am wondering if I set the threshold incorrectly in the config file.
Hi TimH,
Please refer to the BackPressure documentation (also linked in the above post). Look at Table2 that lits these parameters. The valid values are listed.
As the term PercentageDatabaseDiskSpaceUsedHighThreshold states, it's not an absolute value (in memory units) but a percentage.
Thank you for attempting, my problem was it that you solved.
Best regard
Alireza Soleimani
Thank for your Post.Previously i am not able send mails after reading your post i rectified problem.Thank you very much.
This posting was a godsend, it resolved an issue halting email between by Exch2007 & 2003 Interop Connector!
Thanks!
Thanks! Moving the queue DB and logs fixed the issue for me as well.
Hi Bharat, thanks for your blog. It has been interesting reading. I have a similar issue and at this point am unsre if it is related to system resources or lack of. Here is the issue:
From Exchange 2007 server i cannot telnet to any remote domains on port 25.NSLOOKUP queries resolve DNS and MX records ok for these domains from the exchange server. From a second server on the same network i can telnet to domain mx records on port 25 without any issues. It is only from the exchange server i cannot telent out to port 25. I can ping the domain names ok from the exchange server so my DNS looks ok. There is no AV or Firewall software located on this server.
I noticed the following error in the event log however.
Your system is low on virtual memory. Windows is increasing the size of your virtual memory paging file. During this process memory requests for some applications may be denied.
Our paging file utilisation was at about 90% but have increased paging file in accordance with nest practice analyzer ( 8200mb )I have at least 50GB free disk space. Has anyone seen this before? Is it possible the SMTP stack is corrupt? I can recieve e-mail ok but have had to use IIS SMTP connector on another box to deliver e-mail. Any ideas??
Solved the issue for me in EBS, TMG server, moved the Queue to a different volume as per the MS Article, and queues are now operational without the BackPressure Issue.
Thanks Bharat for your post. This came in really handy this morning!
Very useful tip. Thanks a lot.
very cool post
Very good post. Thanks a lot.
Woot! Thanks, that saved my bacon. I was able to get the fix in before any of our lawyers saw that they hadn't received emails for 1/2 an hour....
You are a star
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