Database Concepts › Physical Structures › Segments › Areas and Pages

Areas and Pages

The physical characteristics of the areas identified in the schema are defined in a segment. An area contains record occurrences stored in blocks, or pages, of the database. A page is a block of data whose format is dictated by CA IDMS. When data is read from or written to a database, an entire page (or block) of data is transferred at one time.

An area definition specifies the page size and number of pages in the area. Each page within an area is consecutively numbered beginning with the starting page number specified in the area's definition. The following rules apply when defining an area:

• An area can only contain sequentially numbered pages.
• Gaps in the page numbers may occur between areas.
• All areas within a segment must have non-overlapping page ranges.
• All pages in one area must be the same size. (Page sizes can vary from area to area.)

Both the test and production databases at Commonweather, for example, are divided into three areas:

• ORG-DEMO-REGION- Contains organizational information. The JOB, DEPARTMENT, OFFICE, and SKILL record types are assigned to this area. Within the TESTHR segment, the area contains pages 2001 through 3500.
• EMP-DEMO-REGION- Contains all employee-related information except for insurance. The EMPLOYEE, EMPOSITION, EXPERTISE, and STRUCTURE record types are assigned to this area. Within the TESTHR segment, the area contains pages 6001 through 8000.
• INS-DEMO-REGION- Contains insurance-related information. Occurrences of the INSURANCE-PLAN, COVERAGE, HOSPITAL-CLAIM, NON-HOSP-CLAIM, and DENTAL-CLAIM record types reside in this area. Within the TESTHR segment, the area contains pages 10001 through 10500.

The TESTHR database contains a total of 4000 pages among its three areas.