这是因为在过程中用到了dbms_output.put_line()在服务器端输出信息，而serveroutput 的size默认定义为10000bytes。
修改一下size应该就可以了
set serveroutput on 30000
Cause:The stored procedure RAISE_APPLICATION_ERROR was called which causes this error to be generated.
Action:Correct the problem as described in the error message or contact the application administrator or database administrator for more information.
===============================================
ORA-20000：ORU-10027：buffer overflow,limit of 2000 bytes.
$ oerr ora 20000
20000, 00000, "%s"
// *Cause: The stored procedure 'raise_application_error'
// was called which causes this error to be generated.
// *Action: Correct the problem as described in the error message or contact
// the application administrator or DBA for more information.
应该是变量大小超过了dbms_output.putline的最大值。
解决办法：
SQL>set serveroutput on size 1000000
##2014-07-18添加
解决办法2：
在begin后面加上DBMS_OUTPUT.ENABLE(buffer_size => null) ，表示输出buffer不受限制。
如下面的语句是为了获取创建索引语句
set serveroutput on
declare
v_sql varchar2(1000);
v_result varchar2(2000);
begin
for cur_sql in (select 'select dbms_metadata.get_ddl(''INDEX'',''' ||
T.INDEX_NAME || ''',''XXXX'') FROM DUAL' as f_sql
from v$object_usage t
where t.monitoring = 'YES'
AND T.USED = 'NO') loop
begin
DBMS_OUTPUT.ENABLE(buffer_size => null); --表示输出buffer不受限制
execute immediate cur_sql.f_sql
into v_result;
--DBMS_OUTPUT.PUT_LINE(cur_sql.f_sql);
DBMS_OUTPUT.PUT_LINE(v_result);
end;
end loop;
end;
/