手工创建18c CDB

18c For Exadata版本的介质已经发布，作为一名心急的老粉丝，欣喜的发现可以安装在普通的Linux平台。
但是在通过DBCA建库的时候会报ORA-12754错误，不过这也难不倒万能的网络。图形界面不行，我们还可以手工建库，前提是在参数文件中加入下面的参数。

_exadata_feature_on=true

安装好18c做什么？一些PDB的新特性当然是要体验的，可是悲催的发现，PDB中连一些基础的数据字典视图都没有！！！

[ora18c@localhost ~]$ sqlplus '/as sysdba'

SQL*Plus: Release 18.0.0.0.0 - Production on Wed Jun 27 06:29:20 2018
Version 18.2.0.0.0

Copyright (c) 1982, 2018, Oracle.  All rights reserved.


Connected to:
Oracle Database 18c Enterprise Edition Release 18.0.0.0.0 - Production
Version 18.2.0.0.0

SQL> 
SQL> 
SQL> show pdbs

    CON_ID CON_NAME           OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
     2 PDB$SEED              READ ONLY  NO
     3 PDB1               MOUNTED
SQL> alter pluggable database pdb1 open;

Pluggable database altered.

SQL> alter session set container=pdb1;

Session altered.

SQL> desc dba_users
ERROR:
ORA-04043: object dba_users does not exist

开始怀疑是PDB$SEED的问题，但18c的种子库貌似已经不能像12c那样随意open，只能作罢。

无奈之下只能再去翻官方文档，原来问题出在手工建库的过程中。简单的使用创建传统数据库的模式创建CDB数据库，才产生了上述诡异的问题。
根据官方文档，create database创建完控制文件之后，需要运行catcdba.sql脚本创建CDB相关的对象，然后再跑catalog.sql等脚本。

@?/rdbms/admin/catcdb.sql

根据提示输入

SQL> host perl -I &&rdbms_admin &&rdbms_admin_catcdb --logDirectory &&1 --logFilename &&2
Enter value for 1: /tmp
Enter value for 2: create_cdb.log

Enter new password for SYS: ********
Enter new password for SYSTEM: ********
Enter temporary tablespace name: TEMP

其实这个问题在建库过程中就已经有提示，只是没有注意。

2018-06-27T06:41:39.961677+08:00
Successfully created internal service SYS$BACKGROUND at open
Successfully created internal service SYS$USERS at open
replication_dependency_tracking turned off (no async multimaster replication found)
Starting background process AQPC
2018-06-27T06:41:40.352715+08:00
AQPC started with pid=42, OS id=23014 
PDB$SEED(2):JIT: pid 22024 requesting stop
PDB$SEED(2):Buffer Cache flush started: 2
PDB$SEED(2):Buffer Cache flush finished: 2
2018-06-27T06:41:40.922925+08:00
PDB$SEED(2):While transitioning the pdb 2 to clean state, clearing all its abort bits in the control file.
2018-06-27T06:41:41.482842+08:00
PDB$SEED(2):Endian type of dictionary set to little
2018-06-27T06:41:41.987095+08:00
PDB$SEED(2):Database Characterset for PDB$SEED is AL32UTF8
PDB$SEED(2):Accessing dba_registry_sqlpatch hit error: 942
Accessing dba_registry_sqlpatch hit error: 942

经过一番折腾之后，终于顺利的完成了手工创建18c CDB数据库的任务，搭建起了测试环境。