PostgreSQL Databse Migration to the Latest Version and Help for Database Replication.

Hello,

I am Java Solutions Developer. I have my servers that run PostgreSQL v8.1.11
and they are quit stable.
Recently i was supposed to install a Database Replication tool for the
Databases. I realized that i might have to upgrade my database from v8.1 .11
to v8.4
*1) Would there be any compatibillity issue if i do this migration at one
shot?*

*2)* I have my Java Code that is very vast and it has at many places the
PostgreSQL queries well compatible with the current running version( i.e
v8.1.11), *would the Migration need some changes to be done in the queries?*

*3)* Are there any compatibility mismatch from the version 8.1.11 to the
version 8.4 or 8.3

*4) *Following are the details of the platform on which i have my project
running:
*Operating System:* CentOS v5.1
*Java Version:* v1.4 for the Java Code.
*Web Server:* tomcat4
* PostgreSQL Version: *PostgreSQL v8.1.11

*5) *I want to implement a Master-Slave Replication system, and found that
SLONY-I is the best that matches with PostgreSQL database system. But this
is advisable in an environment where none of the master/slave(s) are having
a problem of being detached from the network or frequent power failures.
Here with my project this is the case.
*Can you suggest a good database replication tool that would replicate my
postgreSQL databases it cud be a master-master DB replication tool as well.
Not a problem.
*I have tried *RubyRep, Bucardo, **but none of these have a stable rpm
release for CentOS version of Linux Operation System*.

Need Help Urgently.

Thanks in advance.

Regards,
Krishna Komarpant
Java Solutions Developer
Online Productivity Solutions Pvt. Ltd.
Verna - Goa
India*
*