General Guidelines for Better Performance

General Guidelines for Better Performance

1．  Avoid unnecessary conversions

2．  Select what you need, avoid select *

3．  Minimize DB2 Sorts, as sorting increases CPU requirements and possibly additional I/O to DB2’s sort work areas.

4．  Use views when join tables, must create index on the join predicates

5．  Examine lock strategy

6．  Prefer static SQL to dynamic SQL

7．  Avoid using scalar functions

8．  About statements

l         Use local predicates

l         Write joins if equivalent to subquery

l         Prefer UNION ALL to UNION which require sorting to eliminate duplicate results

9．  Exploit blocking to reduce the communication expense

10. Limit fetch size

l         OPTMIZE FOR n ROWS

l         FETCH FIRST k ROWS ONLY