Unfortunatelly, safe_mode is not compatible with some OpenX features and its requirements.
It is not possible to install OpenX with php safe_mode disabled!
On shared hosting you could ask support department to turn off the safe_mode.
Also, newer PHP versions do not support safe_mode setting. You should be familiar with other PHP security settings, too (e.g. open_basedir and many others).
In 2.4 and higher versions, OpenX can manage different domains using separated configuration files.
The main "www.example.com.conf.php" configuration file will be located in openx/var folder.
For versions higher than 2.4.2 there is also default.conf.php file with line: realConfig=www.example.com. This ensures using www.example.com.conf.php config file as default one for any domain loading OpenX files other then www.example.com.
Every time when you generate invocation tag the "n" value will be changed even for the same zone. It represents a random generated string for cookies' name.
The cookies keep information about the banner that is shown so each invocation tag on a single page should have a unique value for the "n" variable.
This way will ensure that click on the banner will redirect a user to the valid destinatoin. Invocation tag should have the same "n" value in itself, e.g. image and link tag need to use the same value for "n" variable.
It is recommended to disable maintenance during OpenX installation upgrading
There are two types of OpenX maintenance:
1) Scheduled Maintenance
2) Automatic Maintenance
In order to disable OpenX Scheduled Maintenance you should make changes in your cron job in order to prevent its triggering. On most systems it's enough to comment the line out with # at the beggining of the line.
During upgrading, OpenX create many temporary tables. These tables usually starts with z_ followed by many random characters.
If the upgrading process passed without any issues and OpenX works fine next few days you are free to delete tables with z_ prefix.
You can delete OpenX z_ tables using user interface
1) Login as Administrator (read here how to login with administrator privileges in OpenX)
2) Click 'Product Updates' admin tab
3) Choose "Manage Past Updates and Backups"