At the creation of internal tables what is the criteria configuration of the value of an occurs? | SAP ABAP

What we have to do for configuring the value of an occurs is to make optimizations and for this we have to keep in mind some things like:
a) The default declared size will be maintained in the roll area – faster program access.
b) The whole data area of the application will be 64 kilobytes.
c) The data inserted that is bigger than the default size is deposited in the roll file- the program is accessed slow.
More, prior to deciding to do an optimization we have to analyze the rates of access and the volume .