In-Memory Database Guide : Calculating storage requirements
  
Calculating storage requirements
This section gives you information that helps you estimate how much memory or disk space is required to store a table and its indexes in memory or on disk.
The formulas given here are not precise, for example, because of the following reasons:
solidDB® compresses some data.
Variable-length data (for example, VARCHAR) requires different amounts of space, depending upon the actual lengths of the values stored.
The in-memory data structures do not necessarily store the same number of pointers for every record.
In the formulas in this section:
It is assumed that the data is not compressed, and there are the maximum number of pointers. Thus the results that you get by using these formulas are conservative - that is, the formulas typically overestimate the amount of space required.
The notation sum_of(x) means to take the sum of the sizes of each x. For example:
sum_of(col_size) means to take the sum of the sizes of each of the columns in the table or index.
sum_of(index_sizes) means to take the sum of the sizes of all of the indexes on the table.
See also
Calculating storage requirements for disk-based tables
Calculating storage requirements for in-memory tables
Column sizes against column type
Measuring memory consumption