pdb$seed种子库，默认打开模式为read only

如果要修改pdb$seed的状态，则需在当前会话修改"_oracle_scripts"为true

1. SQL> alter session set "_oracle_script"=true;
   
2. 
   
3. Session altered.
   
4. 
   
5. SQL> alter pluggable database pdb$seed close immediate;
   
6. 
   
7. Pluggable database altered.
   
8. 
   
9. SQL> alter pluggable database pdb$seed open;
   
10. 
    
11. Pluggable database altered.
    
12. 
    
13. SQL> show pdbs
    
14. 
    
15.     CON_ID CON_NAME             OPEN MODE RESTRICTED
    
16. ---------- ------------------------------ ---------- ----------
    
17.      2 PDB$SEED             READ WRITE NO
    
18.      3 PDB1              MOUNTED

pdb$seed可以是open状态，但是建议你不要在pdb$seed中写入数据，它就是个模板，当你通过pdb$seed模板创建新的pdb时，数据会继承到新的pdb，有这个需求还可以，没有这个需求的话会造成数据泄露的风险

似乎和那个隐含参数无关，在PDB$SEED下将该参数设为FALSE，不是也可以吗：

SQL> show pdbs;

CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ WRITE NO
SQL> alter session set "_oracle_script"=false;

Session altered.

Elapsed: 00:00:00.00
SQL> shut immedate;
SP2-0717: illegal SHUTDOWN option
SQL> shutdown immediate;
Pluggable Database closed.
SQL> startup;
Pluggable Database opened.
SQL> show pdbs;

CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ WRITE NO