实验环境创建了两个PDB，本实验实现在开启数据库时，实现pluggable database PDB2自启动：
原始环境：
SQL> shu immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 943718400 bytes
Fixed Size 2931136 bytes
Variable Size 650118720 bytes
Database Buffers 285212672 bytes
Redo Buffers 5455872 bytes
Database mounted.
Database opened.
SQL> select name,open_mode from v$pdbs;
NAME OPEN_MODE
------------------------------ ----------
PDB$SEED READ ONLY
PDBYCR MOUNTED
PDB2 MOUNTED
SQL>
创建trigger：
SQL> CREATE TRIGGER open_pdb_pdb2
2 AFTER STARTUP
3 ON DATABASE
4 BEGIN
5 EXECUTE IMMEDIATE 'alter pluggable database pdb2 open';
6 END open_all_pdbs;
7 /
Trigger created.
SQL> shu immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 943718400 bytes
Fixed Size 2931136 bytes
Variable Size 650118720 bytes
Database Buffers 285212672 bytes
Redo Buffers 5455872 bytes
Database mounted.
Database opened.
SQL> select name,open_mode from v$pdbs;
NAME OPEN_MODE
------------------------------ ----------
PDB$SEED READ ONLY
PDBYCR MOUNTED
PDB2 READ WRITE
已实现pdb2的自启动，可以通过修改trigger脚本中的sql语句实现启动不同的pdb或者实现所有pdb的自启动，脚本如下：
CREATE TRIGGER open_pdb_pdb2
AFTER STARTUP
ON DATABASE
BEGIN
EXECUTE IMMEDIATE 'alter pluggable database pdb2 open';
END open_all_pdbs;
/
观察alert日志中有如下消息：
Opening pdb PDB$SEED (2) with no Resource Manager plan active
alter pluggable database pdb2 open
Database Characterset for PDB2 is WE8MSWIN1252
Due to limited space in shared pool (need 6094848 bytes, have 3981120 bytes), limiting Resource Manager entities from 2048 to 32
Opening pdb PDB2 (4) with no Resource Manager plan active
Pluggable database PDB2 opened read write
Completed: alter pluggable database pdb2 open
Starting background process CJQ0
Completed: ALTER DATABASE OPEN