IIS caches memory blocks, called free memory blocks, for active server page execution. When memory blocks are deallocated within IIS they are moved from the used memory list to the free memory list and retained by IIS for reuse. AspMemFreeFactor specifies the ratio, in percent, of free memory blocks to used memory blocks. When the ratio of free blocks to used blocks exceeds the value of this parameter, free blocks are released by IIS and returned to the virtual memory pool. For example, a value of 500 will cause IIS to release memory when the free memory list is 5 times (500% of) the length of the used memory list.
If your server is performing many tasks in addition to running active server pages under IIS, you may wish to set this parameter low. If your server is primarily dedicated to serving ASP pages, a higher value for this parameter will improve performance. A value of zero eliminates IIS memory block caching for ASP page processing and is not recommended.
If this parameter is changed, the change will not take effect until the Web server is stopped and restarted.
The following table describes this property:
| Data type | Long |
| Default value | 50 (percent) |
| Default inheritance | Inheritable |
Accessible by IIS Admin Objects:
| IIsWebService | IIsWebServer | IIsWebVirtualDir | IIsWebDirectory |