What is the IBM i Database?
IBM i has a database which stores data in files. These are called physical files.
The Physical file stores the actual data.
The data is written to a physical file in arrival sequence. This data can be accessed by RRN (relative record number) where the first entry on the file (also known as a table) is relative record number 1. ie: the first record in the file. The next record is RRN=2 then RRN3 and so on.
If you want to access the data using a sequence of something on the file (for example CUSTOMER sequence) then you would design and create a logical view of this physical file specifying that you want it sequenced by customer.