当我在pl/sql中查询某个表的详细字段信息的时候，报了这样一个错误
sql语句为：

select A.column_name name,A.data_type datatype,A.data_length,
A.data_precision 整数位, A.Data_Scale 小数位,
A.nullable isnullable,A.Data_default 缺省值, c.constraint_name,
B.comments comments from user_tab_columns A,user_col_comments B ,user_constraints C
where a.COLUMN_NAME=b.column_name and A.Table_Name = B.Table_Name and (A.TABLE_NAME=c.table_name and c.constraint_type='P')and
A.Table_Name='" + name + "'

错误是：

dynamic performance tables not accessible,
automatic statistics disabled for this session 

you can disable statistics in the preference menu,or obtain select
priviliges on the V$session,v$sesstat and v$statname tables

解决方法是：
用dba执行下面这句或者在pl/sql中找到username，然后在edit中选择“System privileges”tab，增加一个“select any dictionary”权限。

grant SELECT ANY DICTIONARY to username;