Space Management › Area Space Management

Area Space Management

What is an Area?

A CA IDMS database is divided into one or more areas. Each database area is a named subdivision of addressable database storage. Each area can contain one or more record types, according to varying processing requirements, but all occurrences of a particular record type must be in the same area.

Managing Space in an Area

To manage space in an area, CA IDMS/DB keeps track of available space on each page. CA IDMS reserves selected pages called space management pages (SMPs) for this purpose. The first page in each area is an SMP. Depending on the number and size of pages in the area, CA IDMS may reserve additional SMPs throughout the area.

Since you frequently assign several record types to an area, data pages in these areas are typically filled with record occurrences of different record types and the occurrences' corresponding line indexes. For example, in the sample employee database, the DEPARTMENT, JOB, OFFICE, and SKILL records are all assigned to the ORG-DEMO-REGION area. Thus, occurrences of all of these record types can be stored on the same page.

Sample Page

The following drawing shows a sample page in the ORG-DEMO-REGION. Typically, except for the header and footer, a page in an area is filled with occurrences of different record types. Page 7130 in the ORG-DEMO-REGION area contains occurrences of the OFFICE, JOB, and DEPARTMENT record types.

Space Available

To manage space, CA IDMS/DB keeps track of the available space on each page. The space available is maintained in the following locations:

• SR1 records—System records in each page's header which contain the space available count for the page
• Space management pages (SMPs)—One or more system-reserved pages which contain entries that indicate whether each page (in a range of pages) is empty or full

SR1 records and space management pages are discussed separately next.