Locking oracle table data

Question

I have a 3 tables which contains some crucial accounting data. Now I want to lock the data in those tables for 1 financial year(within a period). Locking data refers to not being able to insert, update or delete the data. But i need to view them time to time and my crystal report use that table too. I can restrict the user in my application. But accidently it may happen sometime. You know sql, a single query can modify or delete the whole table. I just want to protect the data even if any accidents happened.
Can I really do that.
My oracle version is 8i.
Thanks in advance

Answer 1

1. If you are using 11g Release 1 then you can :
alter table table1 read only;
alter table table1 read write;
2. Trigger
Source:http://www.devx.com/tips/Tip/29396
Despite that limitation, you can simulate a read-only table by simply preventing all table modifications using a trigger. To do that, create a trigger as follows.
SQL> create or replace trigger emp_sal_read_only
2 before insert or update or delete
3 on emp_sal_tbl
4 begin
5 raise_application_error (-20001, 'Table EMP_SAL_TBL is read only,
You cannot make changes to the data.');
6 end;
7 /
Trigger created.
Here's a test command that tries to alter the data, and the resulting output:
SQL> DELETE FROM EMP_SAL_TBL;
DELETE FROM EMP_SAL_TBL
ERROR at line 1:
ORA-20001: Table EMP_SAL_TBL is read only, You cannot make changes to the data.
ORA-06512: at "SRIDHAR.EMP_SAL_READ_ONLY", line 2
ORA-04088: error during execution of trigger 'SRIDHAR.EMP_SAL_READ_ONLY'
HTH
Girish Sharma