Set application pool recycling settings for better availability SharePoint Server 2007

Another good article here

Follow these recommendations to keep sites up and running, even when you have to recycle processes for application pools.

Note that the periodic recycle is the default, with a period of 29 hours (1740 minutes). This can be an inconvenience, since each recycle would occur at different times of a day, eventually occurring during peak times.

Virtual Memory this is the memory (Virtual Address Space) that the application has used plus the memory it has reserved but not committed. To understand how the application uses this type of memory, you can monitor it by means of the Process – Virtual Bytes counter in Performance Monitor. For instance, if you receive out of memory errors, but less than 800MB are reported as consumed, it is often a sign of memory fragmentation.

Maximum Used Memory This setting sets a threshold limit on the Used Memory. This is the application’s private memory, the non-shared portion of the application’s memory. You can use the Process – Private Bytes counter in Performance Monitor to understand how the application uses this memory.

In the scenarios mentioned before, this setting would be used when you have detected a memory leak which cannot avoid (or is not cost effective to correct). This setting would set a “cap” on how much memory the application is “allowed” to leak before the application is restarted

I noticed the application pool for the main site recycled every few minutes, with the following event in the System log:
Event Type: Information
Event Source: W3SVC
Event Category: None
Event ID: 1077
Date: **
Time: **
User: N/A
Computer: **
A worker process with process id of ‘3848’ serving application pool ‘**’ has requested a recycle because it reached its virtual memory limit.

    This is how to fix

    If you were using 32 bit environment, by default, 2GB of virtual address space is allocated for each 32-bit Windows user mode process. A certain amount of this address space must remain unused for dynamic allocations. Additionally, some operations in Office SharePoint Server require large blocks of contiguous address space to perform dynamic allocations. The longer a process runs, the more fragmented the address space becomes. Because of this, when the size of the Office SharePoint Server worker process exceeds 1.2 GB to 1.4 GB, the process will begin to experience out of memory errors and other anomalous events. As the process continues to consume address space the errors will get worse, eventually resulting in termination by IIS.

To address this issue, we recommend that you set up the following processes on each 32-bit front-end Web server.

For best results you should set IIS to recycle at specific times, and when memory usage reaches specifics levels.

· Configure a virtual memory-based recycle to occur at 1700 MB.

· Configure the memory used recycle to occur at 1000 MB.

· Set the shutdown time limit to at least 300 seconds to allow long running user requests, such as large file uploads, an opportunity to complete.

· Use time-based recycles in environments with regular heavy loads at certain periods of the day. Set a scheduled recycle about 30 minutes before the peak traffic starts.

Failure to configure these settings on 32-bit servers may have an adverse affect on ASP.NET cache management. If you do not set a process memory limit, ASP.NET will calculate one for you. If the user mode address space is 2 GB, ASP.NET will use the lesser value of either 60% physical RAM or 800 MB. This value will be used to determine how aggressively the cache should clean up memory. Setting this value too low results in spending too much time cleaning up memory. Setting it too high allows the process to grow too large and cause OutOfMemory Exceptions and other errors.

We highly recommend that you install front-end Web servers on 64-bit Office SharePoint Server 2007 on a 64-bit operating system, unless you have a significant business reason not to.

Important: In a 64-bit environment, the default values for process recycling when running are generally sufficient; we do not recommend that you change them.

For more information about recycling worker processes, seeConfiguring Worker Processes for Recycling (

For more information about Overlapped Recycling And SharePoint , please refer to the following articles:

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