Physically, an ALLBASE/SQL DBEnvironment is a collection of
files for the storage of databases.
The physical design process helps you compute the storage requirements
for the tables, indexes, and other objects that emerge
at the end of the logical design process.
This chapter describes several steps that
are involved in developing an
appropriate physical design for your DBEnvironments:
Calculating storage for database objects
Calculating storage for the system catalog
Calculating storage for logging
Calculating temporary disk space
Estimating shared memory requirements
Estimating the number of transactions
Before designing physical storage, you must first establish
the logical design of your databases. The layout of the tables,
the number of columns and column sizes, the column data types,
the number and types of indexes,
and the estimated number of rows per table are all factors that
affect physical design. You should also have an idea of how the
the tables are going to be used, since you can design physical
storage to optimize performance.
Physical design also requires an understanding of ALLBASE/SQL files.
Therefore, this chapter also describes the characteristics of
DBEFiles and log files while presenting
guidelines on determining storage requirements. Familiarity with the
MPE/iX
file system will also help you during the physical design phase.
