The Database Block entity
With Database Blocks, you can describe databases both logically and physically, taking into account the characteristics of certain DBMSs.
The definition and description of the logical or physical Segments is ensured by the Segment entity.
The definition and description of the logical or physical relationships between Segments is ensured by the Database Block entity.
A Database Block is a set of Segments, each of which calls Data Elements.
There are three categories of Database Blocks:
- Relational Database Blocks, which describe the links in relational databases in the SQL language
(for example DB2).
A relational database is a set of physical environments (such as table space, dbspace, space, storage-area) that are called
spaces
here. A space is a set of tables. A table is a set of columns. - Network Database Blocks, which describe the relationships in network databases, such as
CODASYL.
A CODASYL schema is a set of records that are constituted of elementary data. The records are linked to each other through sets. A structure is broken down into areas.
A record and a set belongs to one or more areas.
- Hierarchical Database Blocks, which describe tree-like structured hierarchical databases, such as DL/1.
Database generation
The generation of a Database Block generates the Data Description Language (DDL) that corresponds to the Database Block type.
You can replace or complement these generated lines in the -G Lines tab of the Database Block.