1. deploy a rep into report deployment path defined in sourceDir in <oracle_home>\reports\conf\<repserver>.conf

2. make sure the rep can print correctly

3. define two environment ids in <repsrever>.conf, one is UTF8 with NLS_LANG set as AMERICAN_AMERICAN.UTF8, the other is called zhs, with NLS_LANG set to SIMPLIFIED CHINESE_CHINA.ZHS16GBK

4. in the Engine section, add the defaultEnvId 
      <property name="defaultEnvId" value="zhs"/>.
remember to restart the report server whenever this file is changed.