需求：
1．开发一个批次release工单的程序
2．同时，只能有一个Session Release同一个ORG的工单
解决方法：
1．（WHEN-NEW-FORM-INSTANCE）在程序打开时，删除纪录程序运行table因程序异常关闭未清除的纪录
参考SQL :
DELETE program_lock_control a
WHERE program_name = 'RELEASE_WO'
AND NOT EXISTS (
SELECT 1
FROM v$session b
WHERE b.SID = a.lock_sid
AND b.serial# = a.lock_serial
AND b.audsid = a.lock_audsid);
2．（WHEN-NEW-FORM-INSTANCE）判断自己有没有打开了此程序，如已经打开，提示已经打开，关闭本次打开的程序，否则Insert 一笔纪录到控制table.
参考SQL:
SELECT COUNT (1)
INTO :parameter.v_runner
FROM program_lock_control
WHERE program_name = 'RELEASE_WO'
AND user_id = :parameter.user_id;
IF :parameter.v_runner > 0
THEN
show_alert_message ('您不能同时打开多次此程序!');
DO_KEY ('exit_form');
ELSE
SELECT SID, serial#, audsid
INTO v_sid, v_serial, v_audsid
FROM v$session
WHERE audsid = USERENV ('SESSIONID');
SELECT user_name
INTO v_runner
FROM fnd_user
WHERE user_id = :parameter.user_id;
INSERT INTO program_lock_control
(program_name, organization_id, lock_flag, user_id,
user_name, login_time, lock_sid, lock_serial, lock_audsid
)
VALUES ('RELEASE_WO', 0, 'Y', :parameter.user_id,
v_runner, SYSDATE, v_sid, v_serial, v_audsid
);
COMMIT;
End if;
3. （Find when-button-pressed）按下寻找可Release工单的按钮，同样先删除异常退出程序造成的纪录（防止另外一个用户已经打开程序，一个用户异常退出）
参考SQL:
DELETE program_lock_control a
WHERE program_name = 'RELEASE_WO'
AND NOT EXISTS (
SELECT 1
FROM v$session b
WHERE b.SID = a.lock_sid
AND b.serial# = a.lock_serial
AND b.audsid = a.lock_audsid);
4.（Find when-button-pressed）判断用户选择的ORG是否有被他人所定，如有，提示用户不可操作，如没有，则修改控制table,将ORG栏位改为用户选择的ORG，锁定此ORG.
参考SQL:
SELECT COUNT ('*')
INTO v_count
FROM program_lock_control
WHERE organization_id = :header.org_id
AND program_name = 'RELEASE_WO'
AND lock_flag = 'Y';
IF v_count > 0
THEN
show_alert_message
( '同时只能有一个人Release同一Org的工单，目前 '
|| v_runner
|| '正在运行此程序！'
);
RAISE form_trigger_failure;
END IF;
ELSE
UPDATE program_lock_control
SET organization_id = :header.org_id
WHERE program_name = 'BATCH_RELEASE_WO'
AND user_id = :parameter.user_id;
End if;
5. 用户退出时运行，解除锁定
参考SQL:
DELETE program_lock_control
WHERE program_name = 'RELEASE_WO'
AND user_id=:parameter.user_id;
:System.Message_Level := 25;
commit;
do_key('exit_form');