How to assign MongoDB the complete RAM of system? I am trying to run the MongoDB with the full capacity of my system RAM. But I am not getting a way to assign complete RAM of my system. PLease advise me what I can do in the cnfiguration, so that the RAM will take the complete RAM of my system.

The RAM capacity is 32 GB.
After system reserve 28 GB.
I want to assign the MongoDB with atleast 25 GB of RAM from my system.
Kindly, advise me.
You don't need to do anything. MongoD -process will use all available memory automatically. You may not "notice" it, because mongod -process don't eat all your memory, but in reality, all free memory is used to cache data files (data itself and indexes; weight is on indexes). That's why, available memory should be bigger than active data and indexes are.

If you use wiredTiger, data and indexes stays compressed in the memory too and not only on the data-store.