How to fix error: 452 4.3.1 Insufficient system resources Private bytes under pressure

How to fix error: 452 4.3.1 Insufficient system resources Private bytes under pressure

Many people encounter Back pressure errors on their Exchange servers now and then, but when you have a recently new machine freshly installed and your email traffic is not that intense… How can you keep getting Private Bytes errors!?

Well, the answer is simple in many cases: Dynamic Memory

As you probably know, Dynamic memory is not supported or recommended by Microsoft to be used on any Exchange Server. What gives? Who doesn’t love Dynamic Memory? Well, Exchange was not designed with Dynamic memory in mind, but rather, it was designed to use all available memory it could get it’s hands on to improve performance.

So how come Dynamic memory is messing up with my Exchange this time?

I am not expert but the reason seems to be your initial memory allocated to your VM. Most likely Exchange considering it has a fixed amount of memory will initialize its counters and thresholds using a constant amount of memory. Given that scenario, it is no wonder that if you start your VM with 512 mb you can eat up your private memory quite fast even if your physical server has gigs and gigs of RAM. The issue went away when I started using normal (static) allocation of memory rather than dynamic. I also went as far as to play with my previous hypothesis and it worked. I assigned a “high” amount of dynamic memory to start the system with and then dynamic memory takes some of it away if it is IDLE. This has worked fine with me but I would recommend following Microsoft’s recommendations and using static memory. I kind of like living on the “edge” lol.

Hope this helps!

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2 Responses

  1. Thanks so much JCarlos for your solution about the Dynamic Memory, We’ve been struggling with this error on our new Hosted Exchange environment for the last couple of months. We’ve tried assigning more ram and everything but it just keeps complaining. Right now it’s complaining about not having enough Private Bytes even though its been dynamically assigned 5GB of Ram and is only using 3.5GB. I will change the Startup Ram to 4GB and leave it still on Dynamic memory so that I can actually increase the memory usage as needed.

    P.S. You’ve got a load of information on this site, how do you find the time to write it all and where do you get all your ideas. Are you in an IT position currently?

    • JCarlos says:

      Yeah, I learned the hard way as well to listen to Microsoft when they advice not do so something. I might suggest if you still want to use dynamic memory assigning a starting memory close to the average RAM your VM uses. The purpose is twofold: first as you point out the private bytes issue but secondly dynamic memory allocation begins well after your computer has booted so having plenty of resources to complete the start up tasks helps a lot. Later on Dynamic Memory will remove the excess RAM according to the usage of it. I suggest this for all the VMs you may have (many leave the 512 mb. that comes by default and that causes sometimes issues and for sure longer boot times than it should). And if it is going to use 5 gb anyway, might as well let it start with that much. That way Exchange also anticipates to have that much available.

      Sadly is not that I have the time but that I need to document the issues I encounter and solutions as it seems they come back every now and then. Searching all over the place is more time consuming that writing about it. Also, I figured others might benefit from that information as well so that’s where most of it comes from. Currently I do some IT work, but once the systems are stable I focus on areas of strategy and operations for the business (as we are a small business). Glad to know this post helped you!

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