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5 SSL 5.1 Introduction
The schema DDL is used to describe the logical structure of the data ; the Storage Structure
Language SSL is used to specify the physical storage structure whe n storing data and
logical relationships between data. The definition of the physical storage str ucture is
optional. If it is omitted, UDS/SQL applies the default values. The user can infl uence the
storage space requirements for the data and especially the syste m run-time behavior in
future applications when defining the storage structure.
Designing the storage structure involves the following steps:
1. Declaring the population
2. Defining the linkage of records
3. Determining the placement of member records, tables and hash areas
4. Determining the extent of table reorganization
Each of these steps is dealt with below in a separate section, whi ch also explains the default
cases. These sections are preceded by a description of the methods UDS/S QL uses for the
physical representation of the logical data structure.
The metalanguage used is described on page 22, and the general syntax rules are summa-
rized on page 234.
You compile the SSL using the SSL compiler. For information on operating the SSL
compiler, please refer to the "Creation and Restructuring" manual, Compiling SSL).