What's mean Oracle PE lock from v$lock?

今天同事维护一个数据库，说观察到大量的PE锁竞争:

14:44:34 SQL> select * from v$Lock;

ADDR     KADDR           SID TY        ID1        ID2      LMODE    REQUEST      CTIME      BLOCK
-------- -------- ---------- -- ---------- ---------- ---------- ---------- ---------- ----------
.....
909C43A8 909C43B8          8 PE          0          0          0          6       5174          0
909C43E4 909C43F4         12 PE          0          0          0          6       2688          0
909C454C 909C455C         14 PE          0          0          0          6       1024          0
.....
909C57D0 909C57E0         17 PE          0          0          0          6      17215          0
909C4498 909C44A8         20 PE          0          0          0          6       9887          0
8D75C89C 8D75C8B0         23 TM      13312          0          3          0         18          0
909C46F0 909C4700         27 PE          0          0          0          6      17896          0
909C44D4 909C44E4         33 PE          0          0          0          6      14065          0
909C445C 909C446C         35 PE          0          0          0          6         50          0
.....
909C4588 909C4598         45 PE          0          0          0          6      15619          0
909C4A74 909C4A84         48 PE          0          0          0          6      17877          0
.....
909C45C4 909C45D4         55 PE          0          0          0          6      13485          0
909C49FC 909C4A0C         57 PS          1          2          4          0     100519          0
909C47A4 909C47B4         60 PE          0          0          0          6      17871          0
909C46B4 909C46C4         62 PE          0          0          6          0      17930          1
909C4678 909C4688         68 PE          0          0          0          6      17877          0
.....
909C481C 909C482C         70 PE          0          0          0          6      17646          0
909C4858 909C4868         75 PE          0          0          0          6       6290          0

105 rows selected.

而且进程62居然还Block了其他进程。
PE类型锁定此前居然从未见过，搜索一下Metalink，在一篇回复中找到如下说明:

Generally PE (Parameter Enqueue??) is used only when you change the system parameters dynamically.

看来PE似乎是Parameter Enqueue的缩写，动态修改系统参数可能引起这一锁竞争。
问同事果然修改了一个动态参数，而且hang住了，ft，杀了进程也不管用。

再等一会，数据库居然挂了，这下彻底，赶快重起。