To upgrade phpBB properly without problem, I make a detailed upgrading plan. I would like to share it with you.
1. Disable forum board.
It is important to make the board clean. And keep resource usage low.
The most important part is backup.
2.1. Database backup
2.1.1. phpBB own tools
Admin Control Panel > Maintenance > Backup
Complete backup with gzip, including all tables, save and download.
(if your board has a lot of posts, the index table is very big. I prefer to clean the index first. Just like me, index table is about 200MB)
2.1.2. phpMyAdmin tool
Login your own phpMyAdmin web tool for MySQL database. Select your database and click Export all tables. My exported file is about 50MB.
2.2. Backup all phpBB 3.0.4 files.
SSH your host.
tar czvf forum.tar.gz ~/your.forum/
3. Download “Automatic Update Package”.
For upgrade, I like this package. It can merge your previous changes or mod on you old phpBB when doing upgrading.
wget the package.
tar xjf phpBB-3.0.4_to_3.0.5.tar.bz2
cp -r ./install/ ~/your.forum/
start upgrade following the upgrading wizard.
After it. Rename the install folder or delete it.
Enable the board.