Inventory Data Loader failed to process the file D:\Program Files\Microsoft Configuration Manager\inboxes\auth\dataldr.box\Process\HDD6EP0U.MIF because it is larger than the defined maximum allowable size of 5000000.
Solution: Increase the maximum allowable size, which is defined in the registry key HKLM\Software\Microsoft\SMS\Components\SMS_INVENTORY_DATA_LOADER\Max MIF Size (the default is 5 MB), and wait for Inventory Data Loader to retry the operation
This is an easy fix.
On the CM12 Site Server, open regedit.exe.
Drill down to HKLM\Software\Microsoft\SMS\Components\SMS_INVENTORY_DATA_LOADER.
Find Max MIF Size and double click it.
Change the value to 3200000 (Hex), which is 50 MB. By the way, the actual default value is 4c4b40 (hex) or 5000 kilobytes which is just under 5 MB.
Close regedit.exe and clear out any errors/warnings for SMS_INVENTORY_DATA_LOADER.
Now you’re done!
Thanks for http://www.enhansoft.com/blog/change-the-maximum-file-size-of-management-information-files-mif-in-sccm-2012