What is the reason why IBM recommends to take an offline backup and not an online backup when we do version migrations like from V9.1 - V9.5 or V9.5 - V9.7.

according to the information in the following links:
Difference beetween full offline backup and full online backup (12th Response) - Toolbox for IT Groups
Difference beetween full offline backup and full online backup (10th Response) - Toolbox for IT Groups
Difference beetween full offline backup and full online backup (4th Response) - Toolbox for IT Groups
Difference beetween full offline backup and full online backup (3rd Response) - Toolbox for IT Groups

it would appear that the offline backup would allow for a quicker, more accurate restore.

but then I am mainframe oriented.

Restoring an online backup requires rolling forward the logs. Log formats can change from one release to the next.

I don't think that correctly answers my question.

Here is my scenario. I am upgrading a database from 9.5 to 9.7 [AIX] . To take a back up of the database, it takes 2 hours. Incase I need to take an offline backup before the upgrade, the outage time increases. The reason why I am thinking of online backup is to skip the extra 2 hour outage window.

Whatever backup we take, if wee need to backout our changes, we need to recreate an instance under db2 V9.5 and restore the database. For this restore, either online or offline backup should work.

I know that we cannot rollfoward 9.5 log files on to 9.7 database but at the same time, we cannot restore 9.5 backup on to 9.7 instance - so what is the point in taking offline backup ?

Andy, do you mean, we can restore 9.5 database backup on to 9.7 instance?

Yes you can. As long as it is an offline backup.

Andy

Okay. I have an offline backup which was taken a day before. Probably I can take an incremental offline backup te reduce the outage window.