场景：

　　一用户YDL在下PO单的时候突然断电(或死机)，PO单录到一半。重新打开此PO单后，无法修改订单数据。

　　提示：Could not reserve record [2 tries]. Keep trying?
 

在metalink上搜索，找到如下信息：

fact: Oracle Purchasing
fact: POXPOEPO - Enter Purchase Orders
symptom: Cannot modify purchase order
symptom: Receive errors when opening Purchase Order form
symptom: Could not reserve record [2 tries]. Keep trying?
symptom: FRM-40501: ORACLE error: unable to reserve record for update or
    delete.
cause: The record in PO_HEADERS_ALL corresponding to the purchase order was
    locked.

fix:
Remove lock on the record in PO_HEADERS_ALL.
To remove the lock bounce the database or kill the session that has the table locked.
the locks can be reviewed in the table v$lock

 --查找头的object_id
 select * from all_objects t
 where t.object_name = 'PO_HEADERS_ALL'--44937      45084
 
 --查找锁信息
 select  * from v$lock t
 WHERE t.ID1 = 44937
 or t.ID1 = 45084;

 --查找行的object_id
 select * from all_objects t
 where t.object_name = 'PO_LINES_ALL'--44965 45088
 
 --查询行的锁信息
  select  * from v$lock t
 WHERE t.ID1 IN (44965,45088);

 --查询阻塞会话和其他信息
select 'blocker('||lb.sid||':'||sb.username||')-sql:'|| qb.sql_text  blockers,
       'waiter ('||lw.sid||':'||sw.username||')-sql:'|| qw.sql_text  waiters
from  v$lock lb, 
     v$lock lw,
     v$session sb,
     v$session sw,
     v$sql     qb,
     v$sql     qw
    
where lb.sid=sb.sid
and  lw.sid=sw.sid
and  sb.prev_sql_addr=qb.address
and  sw.sql_address=qw.address
and  lb.id1=lw.id1
and  sw.lockwait is not null
and  sb.lockwait is null
and  lb.block=1

 --根据上面查询结果查询session表中的信息
 SELECT * FROM v$session where sid in (364,276);
 
 --kill
 alter system kill session '364,63776'; 
 

result：最后该PO单可修改。