The Virtual-Table Interface (VTI) consists of purpose functions,
descriptors, and accessor functions.
Purpose functions
The database server calls user-defined purpose functions
to pass SQL statement specifications and state information to the
access method.
Descriptors
Descriptors are predefined opaque data types
that the database server creates to exchange information with a DataBlade module
or an access method. The Virtual-Table Interface (VTI) provides several
descriptors in addition to those descriptors that the DataBlade
API provides.
Accessor functions
Unlike purpose functions, the Virtual-Table Interface (VTI)
supplies the full code for each accessor function. Accessor functions
obtain and set specific information in descriptors.