Any alternative to MQSeries?

Good day everybody,
I have 2 questions, one question relating to an interface between Oracle 8i DB and DB2 and the other on migrating from 8i to 9i, which I seek your kind assistant on.

Q1
I have an application runs on Oracle9iAS and any transaction take place on Oracle application must update some files in DB2 Simultaneously (as it holds the core data as the main customers DB), to achieve this, I am using MQSeries to send/receive messages from/to and to/from HP-UX/AS400 and I have no problem with this at all if things works fine with the MQSeries. But the problem occurs when MQSeries stops (and this happens many times) and causes discrepancies take me days to rectify. The question here, is there any reliable interface methods or APIs that can be used between DB2 and Oracle knowing that the 2 databases resides in the same place and linked via a LAN (TCP/IP link) other than MQ? I have tried oracle's transparent gateway about 4 years ago and found it difficult to manage, install and maintain a part from its poor performance, as it was very slow with frequent dissections where MQ came to be much convenient for its speed and eas to use.
The application and databases environments as follows:
- Oracle runs on an HP-UX machine OS is Unix 11i
- DB2 runs on AS/400 machine with OS400
- The Application is a web based application developed using Oracle9iAS forms, reports and PL/SQL that runs on another HP-UX machine OS is Unix 11i

Q2
Does migrating from Oracle8i to oracle9i enhance the application performance? And how complicated is it?

Appreciating your help
Alajlan