Global Temporary table and REDO

Question

Dear Friends,
In my production database we are facing problem of excessive redo generation. After initial analysis, we realised that we are using a lot global temporary tables for storing temp data/calculations and they are generating redo.
I know that GTT doesn’t create redo but as it creates UNDO and undo is protected by redo therefore it creates some redo but lesser than normal table.
Solution:
I google and found that if I use direct path insertion (using APPEND hint) into Global temporary table the I can avoid this redo generation as specified in this link (http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:15826034070548)
I tried this solution in my GTT but its not making any difference with APPEND clause. Please check following results. Could you please guide me if I am doing something wrong or any other way to avoid redo on GTT.
JM@ORA10G>insert into JM_temp values(1,'aaaaaaaaaaaaaaaaaaaaaaa');
1 row created.
Elapsed: 00:00:00.00
Execution Plan
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | INSERT STATEMENT | | 1 | 100 | 1 (0)| 00:00:01 |
Statistics
0 recursive calls
2 db block gets
1 consistent gets
0 physical reads
*280 redo size*
918 bytes sent via SQL*Net to client
967 bytes received via SQL*Net from client
6 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
1     rows processed
JM@ORA10G>rollback ;
Rollback complete.
JM@ORA10G>insert * into JM_temp values(1,'aaaaaaaaaaaaaaaaaaaaaaa');
1 row created.
Elapsed: 00:00:00.00
Execution Plan
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | INSERT STATEMENT | | 1 | 100 | 1 (0)| 00:00:01 |
Statistics
0 recursive calls
2 db block gets
1 consistent gets
0 physical reads
*280 redo size*
917 bytes sent via SQL*Net to client
981 bytes received via SQL*Net from client
6 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
1     rows processed

Answer 1

Hi,
I tried avoiding GTT in my code but I realised that they are so tightly integrated that i cannot remove them. Operations which I am perfroming on my GTT are
1. Insertion of data
2. Fetch data from main tables with joins on GTT
3. Update GTT with calculated values.
My understanding it Update steps are generating maximum redo.
Please help me how can i reduce my redo generation in such scenarios.
Thanks.