Shared_Pool 是 Oracle SGA中最复杂的一部分，在分析很多 library cache 问题时，经常会用到转储命令。
oradebug dump library_cache 的常用级别包括 (注意，一定要测试之后再采用，要先看看 library cache 大小，如果库缓存非常大，这个转储的日志可能会是 Huge 的)：
等级1：关键结构的统计汇总信息
等级2：HASH CHAIN 信息
等级4：持有对象结构 Bucket 信息，可以看到一个对象的lock,pin,mutex信息。
等级8：Level 4 + 相关数据块
等级16：Level 8 + 每个对象的 Heap 信息
等级32：Level 16 + 完整的 Heap DUMP
使用 oradebug 可以很方便的转储 library_cache 信息，示范如下：
[oracle12c@cat1 ~]$ sqlplus / as sysdba
SQL*Plus: Release 12.2.0.1.0 Production on Tue Jul 31 10:17:00 2018
Copyright (c) 1982, 2016, Oracle. All rights reserved.
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
SQL> oradebug setmypid
Statement processed.
SQL> oradebug dump library_cache 1;
Statement processed.
SQL> select value from v$diag_info where name like 'Defa%';
VALUE
--------------------------------------------------------------------------------
/oracle12c/db/diag/rdbms/enmo12c/enmo12c/trace/enmo12c_ora_7277.trc
SQL> !
[oracle12c@cat1 ~]$ cat /oracle12c/db/diag/rdbms/enmo12c/enmo12c/trace/enmo12c_ora_7277.trc
Trace file /oracle12c/db/diag/rdbms/enmo12c/enmo12c/trace/enmo12c_ora_7277.trc
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
Build label: RDBMS_12.2.0.1.0_LINUX.X64_170125
ORACLE_HOME: /u01/oracle12c/db/product/12.2.0/dbhome_1
System name: Linux
Node name: enmotech
Release: 3.10.0-514.6.2.el7.x86_64
Version: #1 SMP Thu Feb 23 03:04:39 UTC 2017
Machine: x86_64
Instance name: enmo12c
Redo thread mounted by this instance: 1
Oracle process number: 8
Unix process pid: 7277, image: oracle@enmotech (TNS V1-V3)
*** 2018-07-31T10:17:07.023214+08:00 (CDB$ROOT(1))
*** SESSION ID:(982.48265) 2018-07-31T10:17:07.023262+08:00
*** CLIENT ID:() 2018-07-31T10:17:07.023270+08:00
*** SERVICE NAME:(SYS$USERS) 2018-07-31T10:17:07.023277+08:00
*** MODULE NAME:(sqlplus@enmotech (TNS V1-V3)) 2018-07-31T10:17:07.023285+08:00
*** ACTION NAME:() 2018-07-31T10:17:07.023292+08:00
*** CLIENT DRIVER:(SQL*PLUS) 2018-07-31T10:17:07.023298+08:00
*** CONTAINER ID:(1) 2018-07-31T10:17:07.023305+08:00
Processing Oradebug command 'setmypid'
*** 2018-07-31T10:17:07.023346+08:00 (CDB$ROOT(1))
Oradebug command 'setmypid' console output: <none>
*** 2018-07-31T10:17:13.956173+08:00 (CDB$ROOT(1))
Processing Oradebug command 'dump library_cache 1'
LIBRARY CACHE DUMP
LIBRARY CACHE STATISTICS:
namespace gets hit ratio pins hit ratio reloads invalids
-------------- --------- --------- --------- --------- ---------- ----------
SQL AREA 1217773 0.891 21268193 0.985 55850 35229
TABLE/PROCEDURE 881146 0.961 2039858 0.909 76152 0
BODY 192474 0.993 289193 0.994 348 0
TRIGGER 61079 0.986 61077 0.986 2 1
INDEX 152995 0.979 139263 0.816 12489 0
CLUSTER 20622 0.992 20963 0.992 0 0