Built-in access methods
An access method consists of software routines that open files, retrieve data into memory, and write data to permanent storage such as a disk.
A primary access method provides a relational-table interface for direct read and write access. A primary access method reads directly from and writes directly to source data. It provides a means to combine data from multiple sources in a common relational format that the database server, users, and application software can use.
A secondary access method provides a means to index data for alternate or accelerated access. An index consists of entries, each of which contains one or more key values and a pointer to the row in a table that contains the corresponding value or values. The secondary access method maintains the index to coincide with inserts, deletes, and updates to the primary data.
HCL Informix® recognizes both built-in and user-defined access methods. Although an index typically points to table rows, an index can point to values within smart large objects or to records from external data sources.
- The built-in primary access method scans, retrieves, and alters
rows in HCL Informix relational
tables.
By default, tables that you create with the CREATE TABLE statement use the built-in primary access method.
- The built-in secondary access method is a generic B-tree index.
By default, indexes that you create with the CREATE INDEX statement use this built-in secondary access method.