On DB2 V8.2 for AIX you can use
* nothing special and a 16KB or 32KB pagesize.
* Multi-dimensional clustering (MDC) with at 16KB or 32KB pagesize
The advantage of MDC is that it's one table. You get benefits on rollout
(faster deletes of a "partition") and you get fast scans.
MDC is avlaible without extra cost on licence.
* Hash partition the table across multiple database partitions
The advantage of this is scale out across multiple physical machines (if
you choose so).
It requires the Database partitioning feature (significant extra $$/CPU)
and you need to think about the design of your database beyond just this
one table (fnding partitioning keys, etc...).
I would not recommend DPF in an OLTP system just because a single table
is big. DPF works, and works well in OLTP, but it requires careful
layout of your schema.

* UNION ALL views
The advantage can be fast roll-in/roll-out and partition elimination at
runtime as well as compile-ttime.
DB2 is reasonably good about keeping the optimizer plans in check.
Today DB2 supports in access of 100 branches of UNION ALL. I think (!)
you need to run with optimization level 7  to get all the goodies.

In DB2 Viper (ETA pre-announced for "this summer")
You have two more options:
1. DB2 supports more rows per page and more pages per tablespace.
This means you can have a single table of, uh, 16TB and 1.2 trillion
rows if you so desire.
I.e. a simple 4KB pagesize table will do just fine
2. range partitioning
This is the replacement for UNION ALL views. Thousands of partitions are
supported along with special ATTACH and DETACH DDL statements for fast
roll-in, roll-out.

In DB2 Viper we do not recommend UNION ALL views anymore for partitioning.

Cheers
Serge