UniDAC

TUniAlerter Class

A component for sending and receiving database events.

For a list of all members of this type, see TUniAlerter members.

Unit

UniAlerter

Syntax

TUniAlerter = class(TDAAlerter);

Remarks

The TUniAlerter component allows you to register interest in and handle events posted by a database server. Use TUniAlerter to handle events for responding to actions and database changes made by other applications. To get events application must register required events. To do it set the Events property to the required events and call the Start method. When one of the registered events occurs the OnEvent handler is called.

Events are transaction-based. This means that the waiting connection does not get event until the transaction posting the event commits.

Note: not all DBMS supports event notification. Currently TUniAlerter can be used with Oracle, PostgreSQL, and InterBase(Firebird).

TUniAlerter uses the following DBMS-specific features to send and receive events:

Oracle: DBMS_ALERT package;

PostgreSQL: NOTIFY and LISTEN commands;

InterBase: POST_EVENT command;

Inheritance Hierarchy

TDAAlerter
   TUniAlerter

© 1997-2020 Devart. All Rights Reserved. Request Support DAC Forum Provide Feedback