Design decisions

These topics present the choices that you make to optimize the performance and flexibility of the access method that you can create with the virtual-table interface (VTI).

These topics include information about how the access method uses DataBlade API functions, alternative ways to accomplish several SQL tasks, and guidelines for helping users and application developers use the access method in Supply error messages and a user guide.

Store data in shared memory
The access method can allocate areas in shared memory to preserve information between purpose-function calls. To allocate memory, you decide which function to call and what duration to assign.
Access database and system catalog tables
No label-based access control on virtual tables
You cannot have label-based access control on virtual tables or tables with virtual indexes.
Execute a UDR across databases of the same database server instance
User-defined routines (UDRs) used as virtual-table interface (VTI) access methods can have built-in UDT parameters and returned data types across multiple databases of the local database server. You can implicitly and explicitly execute a UDR (written in SPL, C, or Java™) across databases with built-in data types and user-defined distinct types whose base types are built-in data type parameters and return types.
Handle the unexpected
The access method can respond to events that the database server initiates, and to errors in requests for access-method features that the database server cannot detect.
Data definition statements
Process queries that involve a virtual table
This section describes various options for processing a SELECT statement, or query, that involves a virtual table.
Enhancing performance
To enhance performance, the access method can take advantage of executing parallel scans, inserts, deletes, and updates, and buffering multiple rows.
Support for data retrieval, manipulation, and return
This topic affects the design of am_getnext, am_insert, am_delete, and am_update.
Supply error messages and a user guide

Parent topic: Virtual-Table Interface Guide

Related concepts:

Purpose functions

Related reference:

Choose features for the access method