optimizer.txt

You can take backup of Optimizer file in your backup folder after Optimizer file build up. 
This might help you if optimizer file gets corrupted. You can save the number of hours 
for building new optimizer file if you have this file. You can restore backup in case of 
Optimizer corruption. You need to remove corrupted .opt file & place Optimizer backup file
in your Optimizer path (the default path is %AppData%\QODBC Driver for QuickBooks\Optimizer). 
After restoring .opt file you need to run sp_optimizeupdatesync ALL for getting delta changes.
This command will synchronize the all table data with the QuickBooks data file using changed and
deleted data. It is useful for making sure that the optimizer is up to date with
the QuickBooks company file.

Optimizer enhancements:
https://stackoverflow.com/questions/35104497/qodbc-performance-optimizations/35130934#35130934