Oracle 11g下重现library cache lock等待事件

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从下面的例子中可以看到，在生产数据库中对象的重新编译会导致library cache lock，所以应该尽量避免在业务高峰期编译对象。如果是package或过程中存在复杂的依赖关系就极易导致library cache lock的出现，所以在应用开发的过程中，也应该注意这方面的问题。

session1:

SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE 11.2.0.1.0 Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production

SQL> create or replace procedure pining

is
begin
null;
end;
/
SQL> create or replace procedure calling
is
begin
pining;
dbms_lock.sleep(200);
end;

session2:

alter procedure pining compile;

session3:

drop procedure pining;

session4:

SQL> select sid, event,wait_class, seconds_in_wait
2 from v$session_wait w
3 where w.WAIT_CLASS <> 'Idle';
SID EVENT WAIT_CLASS
---------- ---------------------------------------------------------------- ----------------
6 library cache lock Concurrency
132 library cache pin Concurrency
191 SQL*Net message to client Network

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