Setting > Administration – Data performance

• Query which takes more than 3 second to run can be either optimized or not.
• Those Query will be in this view and admin get option to optimise
• You can Optimize the query or remove optimization if the value of optimization impact is not as its need to be.
• Optimise value is either 0, Positive or negative.
  if 0 the query is not optimized
  if value is negative then , value is getting optimized This values indicate an improvement in query performance
  if value is positive then, positive values reveal that the optimization is actually degrading performance
• In Positive value case Optimization can be removed.
• An optimization applied one week ago that has a value of -10% suggests a 10 percent improvement in query performance.
• In backend, Optimization task make the view as indexed view and thus this help in retrieving data more fast.
• If you want to see if an optimization was run, visit Settings > Systems Jobs where you will be able to see the process trigger by the OPTIMIZE button and job status. Take into account that optimization might not be being applied even if its system job appears as completed, the reason is that the indexing process will take place in the back-end storage engine and that is not reflected by the System Jobs view. Depending on entity table size optimizations, this can take more than two hours to have full effect.
•  Data performance option is not available in Sandbox Online Instance

Links to Refer :

https://technet.microsoft.com/en-us/library/mt718506.aspx

https://www.powerobjects.com/2017/10/30/managing-your-data-performance-in-dynamics-365/