Purpose-function flow

The diagrams in this section show, for each SQL statement, which purpose functions the database server executes. Use the diagrams to determine which purpose functions to implement in the access method.

The complexity of the purpose-function flow for each statement determines the order in which the statement appears in this section.

This section also describes the oncheck utility interface.

Tip: The database server invokes the am_open and am_close purpose functions once per fragment for the first SQL statement that references a new virtual table. After the initial calls to am_open and am_close, the database server resumes the normal purpose function flow for the active SQL statement.

The following statements result in an additional call to am_open and am_close before the INSERT statement:

CREATE TABLE newtab (...) USING myvti
INSERT INTO newtab VALUES (....)