DB2 FOR LUW / DB2FORLUW / A50 - DB2

Under rare scenario, DB2 might produce a suboptimal plan for SQL 
queries leading to performance degradation. 
The problem can be seen for the following conditions: 
1) The query is an UPDATE or DELETE 
2) The query references a scalar subquery either within the SET 
clause of the UPDATE or the WHERE clause of the DELETE statement 
3) The scalar subquery has one or more correlated predicates 
4) There is no primary key or unique key on the set of 
predicates in the scalar subquery 
 
eg. 
UPDATE t1 set t1.c1 = (select c1 from t2 where t1.c2 = t2.c2) 
where exists (select c1 from t2 where t2.c2 = t1.c2); 
 
DELETE from t1 where t1.c1 = (select c1 from t2 where t2.c2 = 
t1.c2);

not known / see Local fix

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

02.10.2015
05.02.2016
05.02.2016