Oracle 12C -- CDB的启动过程

以启动DB12为例子

$ sqlplus '/as sysdba'
SQL*Plus: Release 12.1.0.2. Production on Sun Nov  :: 

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

Connected to an idle instance.

1.nomount阶段

SQL> startup nomount;
ORACLE instance started.

Total System Global Area  bytes
Fixed Size                   bytes
Variable Size              bytes
Database Buffers           bytes
Redo Buffers                bytes
SQL> select name,open_mode from v$pdbs;

no rows selected

2.mount阶段：打开控制文件，Root和pdbs都被mount起来

SQL> alter database db12 mount;                

Database altered.

SQL> select name,open_mode from v$pdbs;

NAME                           OPEN_MODE
------------------------------ ----------
PDB$SEED                       MOUNTED
PDB1                           MOUNTED
PDB2                           MOUNTED

3.open阶段：root被打开，pdbs仍然是mounted状态，seed pdb处于只读状态

SQL> alter database db12 open;

Database altered.

SQL> select name,open_mode from v$pdbs;

NAME                           OPEN_MODE
------------------------------ ----------
PDB$SEED                       READ ONLY
PDB1                           MOUNTED
PDB2                           MOUNTED

4.打开PDB

SQL> connect sys@pdb1 as sysdba
Enter password:
Connected.
SQL> alter pluggable database pdb1 open;

Pluggable database altered.

SQL> select name,open_mode from v$pdbs;  

NAME                           OPEN_MODE
------------------------------ ----------
PDB1                           READ WRITE

SQL>