ora817 sga problem

Hi

Oracle users from time to time have an error "invalid column name" on select from database. That invalid column is usually function based column. I read thread about "cursor_space_for_time" but I still don't know is it reason. Database is used by 30-40 users in time now , but previously was 120-130 users and locally guru tunes database to this value of users . I thing some values are too big and this is the reason of the error .. am I right ?

I found a solution like that :

SELECT sharable_mem/VALUE FROM
(select sum(sharable_mem) sharable_mem

 from sys.v_$sqlarea a, dba_users b
where a.parsing_user_id = b.user_id) A,
(select value from v$sga where name like 'Var%')

when a result is larger than 0.3 (usually in my db is 0.7) i should flush a shared pool (alter system flush shared_pool) .. I'm not sure that is good idea ..

an error occurs mostly in users which have big value of sum(sharable_mem).

Which parameters should I check ?

If someone want help i can paste some fragments of init.ora :)

Regards

-- 
Pozdrawiam
Morff
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