原因
导入数据时报错以下错误，这是因为原来的数据库是GBK的，每个汉字两个字节，但新数据库是UTF-8的，每个汉字是三个字节，导致超过长度了。
ORA-12899: value too large for column (actual: 27, maximum: 20)
解决
开始-->运行-->cmd,之后输入:"sqlplus /nolog"，进入"SQL>"的提示，按照下面给出的命令依次执行就可以了：
SQL>connect username/password as SYSDBA; SQL>SHUTDOWN IMMEDIATE; SQL>STARTUP MOUNT; SQL>ALTER SYSTEM ENABLE RESTRICTED SESSION; SQL>ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0; SQL>ALTER SYSTEM SET AQ_TM_PROCESSES=0; SQL>ALTER DATABASE OPEN; SQL> ALTER DATABASE CHARACTER SET ZHS16GBK ; ALTER DATABASE CHARACTER SET ZHS16GBK; *ERROR at line 1: ORA-12712: new character set must be a superset of old character set 报字符集不兼容，此时下INTERNAL_USE指令不对字符集超集进行检查： SQL>ALTER DATABASE CHARACTER SET INTERNAL_USE ZHS16GBK; SQL>SHUTDOWN IMMEDIATE; SQL>STARTUP;
