Plz suggest how to optimized

Question

Hi i have following scenerio:
Oracle Database 10g Release 10.2.0.4.0 - 64bit Production
table structure
SQL> desc PRODUCTION_HISTORY
Name Null? Type
FK_COMPANY_ID NOT NULL NUMBER(10)
PRODUCTION_HISTORY CLOB
SQL> UPDATE
PRODUCTION_HISTORY
SET
PRODUCTION_HISTORY='this is testing' ||
PRODUCTION_HISTORY
WHERE FK_COMPANY_ID=67836 2 3 4 5 6 ;
1 row updated.
Execution Plan
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)|
| 0 | UPDATE STATEMENT | | 1 | 92 | 1 (0)|
| 1 | UPDATE | PRODUCTION_HISTORY | | | |
| 2 | INDEX UNIQUE SCAN| SYS_C00205110 | 1 | 92 | 1 (0)|
Note
- 'PLAN_TABLE' is old version
Statistics
65 recursive calls
682 db block gets
208 consistent gets
31 physical reads
256724 redo size
823 bytes sent via SQL*Net to client
806 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
1 rows processed
plz guide how to optimize???

Answer 1

Well you can't get much better than the index unique scan the plan shows.
So my assumption was that a large CLOB value is being updated, prefixed with something new, which requires a lot of block accesses and reorg.
Can you check the length of that CLOB value?
select length(production_history)
from production_history
where fk_company_id = ....By the way, the fk_company_id value (67836 2 3 4 5 6 ), looks strange with all the spaces in between. That is supposed to be a number value?