关于oracle字符集的介绍参考：http://blog.csdn.net/cymm_liu/article/details/7605081 （此博客也包含了一种修改字符集的方法，但是不建议使用）
今天我们为了解决这个问题：http://blog.csdn.net/cymm_liu/article/details/12013243
采用oracle 的字符集转换工具DMU来进行操作。。
1、DMU简介
参考：The Database Migration Assistant for Unicode (DMU) Tool (文档 ID 1272374.1)
Oracle Database Migration Assistant for Unicode (DMU) is a unique next-generation migration tool providing an end-to-end solution for migrating your databases from legacy encodings to Unicode. DMU's intuitive user-interface greatly simplifies the migration process and lessens the need for character set migration expertise by guiding the DBA through the entire migration process as well as automating many of the migration tasks. It comes with a scalable in-place migration architecture which significantly reduces the effort and downtime required for data conversion, comparing to conventional export and import migration methods. For post-migration and existing databases already using the Unicode character set, the DMU also has a validation mode, in which it identifies data not correctly encoded in Unicode, thus providing a healthcheck on potential issues with implementation of Unicode in database applications.
New! Oracle DMU 1.2, released in February 2013, supports the new VARCHAR2 data type length limit that has been extended in Oracle Database 12c to 32767 bytes. VARCHAR2 data up to 8191 bytes can now be migrated to Unicode with guarantee to not expand over the limit. As 8191 bytes is more than the original limit of 4000 bytes, all databases freshly upgraded to Oracle Database 12c can be migrated to Unicode with significantly simplified handling of data length expansion issues. Other new features in DMU 1.2 include the support for 64-bit JDK on Windows, a new script CSREPAIR for fixing incorrect database character set declarations, and a Live Update feature to automatically check for future DMU updates and upgrade the existing installation transparently. This release of the DMU is also bundled with Oracle Database 12c in addition to being distributed via OTN. The legacy character set migration utilities CSSCAN and CSALTER are no longer shipped or supported with Oracle Database 12c. Please see the DMU 1.2 Release Notes for changes since the 1.1 release.
Oracle DMU is described in more details in the DMU Data Sheet.
使用步骤：
参考：
http://www.oracle.com/technetwork/products/globalization/dmu/learnmore/start-334681.html
