IMSDB Struture example -


Smallest unit of data that an application can retrieve form a database. Contains one or more fields of data. In other words, Segment is created by similar data items together.

A segment is a combination of one or more data items combined together. A segment is the smallest unit passed from the application program to perform the transaction. In the above example, there are three segments.

  • Company
  • Employee information ( Combination of two data items emp number, emp name)
  • Project information ( Combination of two data items proj number, proj name)

Segment can consists small data items called as Fields. Segment can be created with a single field or a combination of more than one field.

Segment type -

Segment can be of different categories based on the information of it contains. Segment can be of 255 types in the IMS database. In the above example, company, employee & projects are the segment types.

Segment Occurrence -

Segment occurrence is the number of occurrences of segment type. In the database, the segment type should be only one. The Segment occurrence can be unlimited. In the above example, unlimited companies can have same structure defined above.