In IMS DB (Information Management System Database), a logical relationship refers to the association or connection between segments within the hierarchical database structure. These relationships define how segments are related to each other and how they interact within the database. Logical relationships play a crucial role in organizing and navigating through the hierarchical data structure of IMS DB.
There are primarily two types of logical relationships in IMS DB :Parent-Child Relationship :
* The most common type of logical relationship in IMS DB is the parent-child relationship.
* In a parent-child relationship, one segment serves as the parent segment, while another segment is its child segment.
* The parent segment contains one or more occurrences of the child segment, establishing a hierarchical relationship between the two segments.
* For example, in a database containing customer and order information, the "CUSTOMER" segment may serve as the parent segment, while the "ORDER" segment serves as the child segment. Each occurrence of the "CUSTOMER" segment may have multiple occurrences of the "ORDER" segment associated with it.
Set-to-Set Relationship :
* Less common but still used in some IMS applications, set-to-set relationships involve the association between segments at the same hierarchical level, rather than hierarchical parent-child relationships.
* In a set-to-set relationship, segments are related to each other based on common criteria or attributes, rather than hierarchical nesting.
* For example, in a database containing product and supplier information, the "PRODUCT" segment and the "SUPPLIER" segment may have a set-to-set relationship if they share common attributes or criteria, such as product codes or supplier IDs.
These logical relationships define the structure and navigation paths within the IMS database, allowing applications to access and manipulate data efficiently. They enable applications to traverse through the hierarchical structure of the database, retrieve related data, and maintain data integrity and consistency. Logical relationships are defined and managed through the database schema and are essential for effective data modeling and application development in IMS DB.
