查看oracle数据库字符集：

select userenv('language') from dual;
查询结果：
SIMPLIFIED CHINESE_CHINA.AL32UTF8

修改oracle数据库字符集：（在SQL Plus中执行）

sql> conn / as sysdba;
sql> shutdown immediate;
database closed.
database dismounted.
oracle instance shut down.
sql> startup mount;
oracle instance started.
total system global area  135337420 bytes
fixed size                          452044 bytes
variable size                     109051904 bytes
database buffers              25165824 bytes
redo buffers                      667648 bytes
database mounted.
sql> alter system enable restricted session;
system altered.
sql> alter system set job_queue_processes=0;
system altered.
sql> alter system set aq_tm_processes=0;
system altered.
sql> alter database open;
database altered.
sql> alter database character set internal_use UTF8
sql> shutdown immediate;
sql> startup;

注意：gbk编码设置为ZHS16GBK；utf8的设置为AL32UTF8