数据库版本：11.2.4.0

操作系统：AIX 6.1

SQL> drop user PATROL2;

*

ERROR at line 1:

ORA-04021:timeout occurred while waiting to lock object

查看SID 242

kill 掉非本地进程

再次DROP 用户正常

MOS：

CAUSE

This is most likely due to following internal bug:

SQL statements that make use of the new GV$() function would acquire a
librarycache (KGL) lock for session duration. One example of such a SQL statement is:

SELECT c FROM table(GV$(cursor(select count(*) c from
v$active_session_history where is_awr_sample='Y')));

These locks are acquired in shared mode but will block other operations that
require an exclusive mode lock.

If you are seeing exclusive library cache locks against GV$ related objects
where the holder has acquired the lock in shared mode and has executed a
SQL statement that involves a GV$() function then you might be seeing this
problem.

Unable To Drop User Due to Ora-4021 (文档 ID 2325903.1)

SOLUTION

1. Apply  Patch 21293453
   Or use following workarounds:
2. Kill the blocker session
   Or
3. Stop db console (or cloud control)