Narrowed search is the process of retrieving records by gradually narrowing the search processing. In a narrowed search, the ASSIGN LIST statement generates a list, which refers to either saved data or a set of saved data with a temporary name (list name). The list is created during the process so that information can be retrieved by gradually narrowing the search for data by specifying conditions until an appropriate number of data items can be identified.

If an existing list created using known identical or substantially similar conditions is available, processing performance can be improved by using it. When multiple conditions are specified, a search can be performed by combining multiple lists. For details about narrowed searches, see the HiRDB Version 8 UAP Development Guide. Figure 5-12 shows an example of a search using a list.

Figure 5-12 Example of a search using a list

Preparations for performing a narrowed search

Following are the prerequisites for conducting narrowed searches:

Specifications in a system definition

It is necessary that the following two operands related to narrowed searches be specified in the system common definition:

• pd_max_list_users: Specifies the maximum number of users who are to be permitted to create lists.
• pd_max_list_count: Specifies the maximum number of lists that one user will be permitted to create.

For details about the narrowed search operands in the system common definition, see the HiRDB Version 8 System Definition.

Creating a list RDAREA

A list RDAREA can be created with either the database initialization utility (pdinit) or the database structure modification utility (pdmod). For details about list RDAREAs, see the HiRDB Version 8 Installation and Design Guide.