Hello Saravanan,

Using following commands you can backup and restore the database without worrying about the versions.

Backup: pg_dump --host host_name -U USER_NAME --port DB_PORT DB_NAME > path/file_name.sql

Restore: psql DB_NAME -U USER_NAME -f path/file_name.sql

Reference: BACKUP-DUMP-RESTORE

Hi,

I think the easiest way is to upgrade 8.4 cluster instead of migrating one database. Below I provide steps to do that, hope it'll be helpful.

1. Install both PostgreSQLs: 8.4 and 9.1

2. Check that you have two clusters running using the command:
pg_lsclusters

3. Drop cluster 9.1
pg_dropcluster --stop 9.1

4. Upgrade cluster 8.4
pg_upgradecluster 8.4 main

5. It will take some time to upgrade, and copying all your config from old cluster to the new one.

6. Test if it works

7. Drop 8.4
pg_dropcluster --stop 8.4

8. Upgrade to 9.3 eventually. ;)
 

without migrating anything(supposing you stay on the same openerp verison)

you should just make a dump of your db in plain text from your 8.4 postgres server and restore it the same way on the 9.1.