手動重新整理share pool可導致快取序列（cache sequence）不連續/丟失，
dbms_shared_pool.keep可防止sequence cache不被flush share pool清空，
但是不能防止shutdown引起sequence cache清空而導致的sequence斷裂。

C:\>sqlplus scott/[email protected]

SQL*Plus: Release 11.2.0.1.0 Production on Fri Jun 8 18:34:35 2012

Copyright (c) 1982, 2010, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> drop sequence test_seq;

Sequence dropped.

SQL> CREATE SEQUENCE test_seq START WITH 10000 MAXVALUE 2147483647 MINVALUE 1 NOCYCLE CACHE 1000 NOORDER;

Sequence created.

SQL> select test_seq.nextval from dual;

   NEXTVAL
----------
     10000

SQL> select test_seq.nextval from dual;

   NEXTVAL
----------
     10001

SQL> alter system flush shared_pool;

System altered.

SQL> select test_seq.nextval from dual;

   NEXTVAL
----------
     11000

SQL> execute sys.dbms_shared_pool.keep('test_seq', 'Q');

PL/SQL procedure successfully completed.

SQL> select test_seq.nextval from dual;

   NEXTVAL
----------
     11001

SQL> alter system flush shared_pool;

System altered.

SQL> select test_seq.nextval from dual;

   NEXTVAL
----------
     11002

SQL>


REF:
Caching Oracle Sequences [ID 62002.1]