Upgrade log file location


In my previous upgrade from osj 2.4.8-3 to ojs 3.1.2-1 i seemed to lose my upgrade log or I do not know where to find it now that I need to investigate the log.

Could anyone please show me how to retrieve the upgrade process log or if I have to run the upgrade again just to get the log for investigation of upgrade process - i will, in this case how should I store the log out put during the upgrade process? should I just pipe it “>” to a file to save?

Also how do I turn logging to a more verbal/debug level so that I can see more details, should that be configured in php.ini?

Thanks in advance for any help, any suggestions are highly appreciated.