Some Caveats

The use of the IN AUTONOMOUS TRANSACTION DO statement in the database event triggers related to transactions (TRANSACTION START, TRANSACTION ROLLBACK, TRANSACTION COMMIT) may cause the autonomous transaction to enter an infinite loop

The DISCONNECT and TRANSACTION ROLLBACK event triggers will not be executed when clients are disconnected via monitoring tables (DELETE FROM MON$ATTACHMENTS)

Creating a trigger for the event of connecting to the database that logs users logging into the system.The trigger is created as inactive.

CREATE TRIGGER tr_log_connect
INACTIVE ON CONNECT POSITION 0
AS
BEGIN
  INSERT INTO LOG_CONNECT (ID,
                           USERNAME,
                           ATIME)
  VALUES (NEXT VALUE FOR SEQ_LOG_CONNECT,
          CURRENT_USER,
          CURRENT_TIMESTAMP);
END

Creating a trigger for the event of connecting to the database that does not permit any users, except for SYSDBA, to log in during off hours.

CREATE EXCEPTION E_INCORRECT_WORKTIME 'The working day has not started yet.';

CREATE TRIGGER TR_LIMIT_WORKTIME ACTIVE
ON CONNECT POSITION 1
AS
BEGIN
  IF ((CURRENT_USER <> 'SYSDBA') AND
      NOT (CURRENT_TIME BETWEEN time '9:00' AND time '17:00')) THEN
    EXCEPTION E_INCORRECT_WORKTIME;
END