I would suggest you to review the following blog post:
Basically if 32-bit IIS process is used on 32-bit operating system and you could have maximum 2GB amount of memory available. If you are using 64-bit operating system you could have maximum 4GB amount of memory available.
Regarding the memory limits of the application pool, it can have a private memory limit and a virtual memory limit.
Primary memory limit: Maximum amount of private memory (in KB) a worker process can consume before causing the application pool to recycle.
Virtual memory Limit: Maximum amount of virtual memory (in KB) a worker process can consume before causing the application pool to recycle.
Both the above settings are set to 0 by default, which means there is no limit set.
If you are using 32-bit IIS process, by navigating to the Advanced settings of the application pool you could increase the limit of the Virtual Memory (for example: 2GB). If you are using 64-bit IIS process you could decrease the limit to be smaller than 4GB for instance.
You could also discuss these questions with your administrators who would provide further information.
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