Hello all,

Not being a experienced db admin I am looking for some help on the following questions.

1.) Is it possible to gain performance by replacing OR by IN or maybe by BETWEEN in the where clause. I don't think so, because the optimizer should
do what its name suggests: optimize my queries.

2.) I heard that creating many tables in one tablespace decreases performance because there can only be one active access to one tablespace
at a given time. If the tables are created in different tablespaces access can take in parallel. Is that true ?

Any help would be highly appreciated.
A link to a online manual regarding these topics would be great.

Many thanks in advance
mike

While OR and IN predicates may often result in the same execution plan, BETWEEN will most certainly produce a different plan. The best way to prove it is to try.

Yes and no. It may have been somewhat true for DB2 on Z/OS until recently but in general it is not. Tabespaces are logical constructs, while I/O performance depends on physical layout of tablespace containers. You can put containers for multiple tablespaces on a single physical device and thus create a bottleneck. Alternatively, you can have a single tablespace with a single container created on a dual-channel array consisting of a few dozen physical disks and not worry about I/O performance at all.