Defining Segments, Files, and Areas › Planning › Records Per Page

Records Per Page

Maximum Records Per Page Affect Database Page Count

When defining a segment, you can specify the maximum number of record occurrences or rows that can be stored on a database page. The value you assign determines the db-key format, which in turn, affects the highest allowable page number that can be assigned to areas associated with the segment.

What Value Should You Use?

In most cases, use the default number of records per page, 255. This value accommodates a database with page numbers up to 16,777,214. Otherwise, choose:

• A larger value if your database contains very small records and your page size is large.
• A smaller value if your database contains very large records or you need more than 16,777,214 pages in a single database

Maximum Records Per Page Restrictions

You may define a database that has different maximum records per page for its component segments; however, you may not define a database in which components of a set, index, or referential constraint reside in areas with different maximums.

Maximum Records Per Page and Transactions

The same considerations that apply to page groups also apply to maximum records per page:

• All data accessed in a run unit must have the same maximum number of records per page, unless the MIXED PAGE GROUP BINDS option is specified on the DBNAME statement that defines the database being accessed.
• SQL transactions have no limitations in this regard.

Note: For more information about mixing maximum records per page, see Chapter 6, “Defining a Database Name Table".

Maximum Records Per Page and Dictionaries

There are special rules regarding dictionaries and maximum number of records per page.

Note: For more information, see Chapter 6, “Defining a Database Name Table” and Chapter 25, “Dictionaries and Runtime Environments”.