The "Load database into memory" option on the Local Fuzzy Database Properties window enables you to optimize performance by loading the database into the memory of the machine processing a batch.

It is best practice to select this option if there is enough memory available, as this can speed up performance by a factor of ten or more.

If a database contains one million addresses, and each address has three fields, the database occupies around 100 MB of memory.

If this option is not selected, the database is partially stored on disk. This requires less memory, but can affect speed.