Defining a Database Using Non-SQL › Schema and Subschema Compilers

Schema and Subschema Compilers

Schema Compiler

The schema compiler, IDMSCHEM, performs the following functions:

• Accepts as input DDL statements that describe the areas, records, elements, and sets of the database
• Evaluates the syntax and logic of the input
• Places source descriptions of the schema and its components into the dictionary
• Produces a list of the compiler's activities

Subschema Compiler

The subschema compiler, IDMSUBSC, performs the following functions:

• Accepts as input DDL statements that describe the subschema as follows:
  • Identifies selected areas, records, elements, and sets of the database
  • Defines logical records
  • Places restrictions on allowable DML verbs
• Validates the syntax and logic of the input
• Places a source description of the subschema into the dictionary
• Generates a subschema load module and places it into the dictionary
• Produces a list of the compiler's activities

You can define any number of subschemas for each schema. One subschema might include all areas, records, and sets in the schema while another might contain only those areas, records, and sets needed for a program accessing the database. Usually you define one subschema for each group of similar applications that access the database.

Additional Functions of the Compilers

In addition to the functions stated above, SCHEMA and SUBSCHEMA statements can:

• Add, modify, delete, display, or punch a schema or subschema description
• Secure the schema or subschema definition
• Authorize users to issue specific verbs against the schema or subschema definition

Note: For more information about using the schema and subschema compilers, see Chapter 10, “Using the Schema and Subschema Compilers”.