Access methods

This section describes access methods, explains why you create user-defined access methods, and shows you how to create user-defined access methods

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.
User-defined access methods
You can create user-defined primary access methods that provide SQL access to non-relational and other data that does not conform to built-in access methods. For example, a user-defined access method might retrieve data from an external location or manipulate specific data within a smart large object.
Access-method components
When you add an access method to HCL Informix, you add, or register, a collection of C user-defined routines (UDRs) in the system catalog. These UDRs take advantage of the Informix application programming interface (API), the Virtual-Table Interface (VTI).
Access method flow
To apply a user-defined access method, the database server must locate the access-method components, particularly the purpose functions.

Parent topic: Virtual-Table Interface Guide