Oracle 12c：修改PDB的MAX_STRING_SIZE

MAX_STRING_SIZE在12c后支持从4000字节改为32767字节，注意是字节，不是字符。

参考此页面的：

• Increasing the Maximum Size of VARCHAR2, NVARCHAR2, and RAW Columns in a PDB

当前设置：

SQL> show con_name

CON_NAME
------------------------------
PDB1
SQL> show parameter MAX_STRING_SIZE

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
max_string_size                      string      STANDARD

操作，注意脚本都需要在PDB中执行：

connect / as sysdba;
alter pluggable database pdb1 close;
alter pluggable database pdb1 open upgrade;
alter session set container=pdb1;
ALTER SYSTEM SET max_string_size=extended SCOPE=SPFILE;
@?/rdbms/admin/utl32k.sql
SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         3 PDB1                           MIGRATE    YES
alter pluggable database pdb1 close;
alter pluggable database pdb1 open read write;
alter session set container=pdb1;
SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         3 PDB1                           READ WRITE NO

@?/rdbms/admin/utlrp.sql

验证，PDB中改了，根容器没有改：

SQL> show parameter MAX_STRING_SIZE

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
max_string_size                      string      EXTENDED
SQL> connect / as sysdba
Connected.
SQL> show parameter MAX_STRING_SIZE

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
max_string_size                      string      STANDARD