What is 'Safety Cushion'? (86434)

When navigate to Benefit Report | Report Option Screen | Storage Calculation, there is "safety cushion" of 10 % as default value. What does it mean ? What happens if changing it?
 

Since Space Manager with LiveReorg is doing an estimate, and our numbers are not 100% exact, we add a little extra to our size estimate to prevent our size checks from thinking you have enough space for the table and then you run out of room at reorganization time and the reorg job fails.

The safety cushion is what the user feels comfortable with. If you want a closer estimate, you can change it to 0. The safety cushion number does not affect the size of the new table in any way. The only time it’s important is when you are reorganizing a table to a location that has very little free space. If you have plenty of free space, then the new table will always reorganize successfully. If you have barely enough free space, and you reorganize the table with a very small safety cushion, what MIGHT happen is that, at reorganization time, we fail because there isn’t enough space for the new table. With a bigger safety cushion, we would have given you a warning at script generation time, or at the beginning of the job at runtime.