When memory is freed at a given address, the heap manager checks how many contiguous bytes are free around that address. After that check is complete, the heap manager can do one of two things:

• Keep the contiguous memory block committed.
• Decommit the contiguous memory block and mark it as reserved only.

The HeapDecommitFreeBlockThreshold registry key specifies the number of contiguous bytes above which the memory is decomitted (the second option) rather than retained for reuse (the first option).

Note On computers that have one gigabyte or more of RAM, apply the following setting for maximum performance:

On computers that have less than one gigabyte of RAM, do not use the HeapDecommitFreeBlockThreshold registry key unless intense memory fragmentation is occurring.