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An index area provides the physical storage of key values with pointers to the corresponding records in the data area.
The Index Area (IXX) provides fast access to the data. Each database can contain one or more index areas (but normally has only one), which provides accessibility to all data areas within that database. The index allows any table in the database to be retrieved based on the contents of the table. CA Datacom/DB places an entry in the index for each key within each table in the database.
The Index Area is a compound relational index. All key types for a given database are contained in one compound index. The relational index system stores a given key value only once regardless of the number of tables in the databases that contain that key value. Proper selection of keys can optimize data retrieval.
The data areas are the physical storage medium used by databases to store tables. Every data area is a data set or file. The data areas are divided into blocks based on the block size defined to CA Datacom Datadictionary. The data block is the unit of physical transfer between the DASD device and CA Datacom/DB. As you populate your tables, these blocks are populated with multiple rows from one or more tables defined to that data area. Database maintenance, such as backups and loads, is performed on data areas.
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