This summer I was performing an upgrade on a 3.0.2 journal and lost all authors in the process. I saw an entry on this forum by someone with exactly the same problem. Alec was puzzled and wanted to see the database because he could not understand how did happened.
Later I found out what went wrong. In my language (nl_NL) the translation of the installation page says something to the effect that if I want to perform an update on a 2.x version of OJS, then click here.
That was not what I wanted to do. So I looked for the correct way to do the upgrade. I choose the option lower on the page that offers you the possibility to not create a new database. I felt like: okay that should be the way. And with this procedure I did loose the authors, correct.
Later I saw the en_US version of the page and was surprised that here you directly go to the upgrade and that it works without problems. Currently I ignore the 2.x message and everything works fine.
I checked some of the locale.po files and I found that a lot of languages still have this problematic 2.1 message. It may prevent some puzzling questions on this forum if you would amend these messages.
This is the English text:
"<p>If you are upgrading an existing installation of OJS, <a href=\"{$upgradeUrl}\">click here</a> to proceed.</p>\n"
And these are some other languages that explains that this procedure is just for 2.x versions:
"<p>Se stai aggiornando da una installazione OJS 2.x esistente, <a href=\""
"{$upgradeUrl}\">fai click qui</a> per procedere.</p>\n"
"<p>Ako nadograđujete postojeću instalaciju OJS 2.x, <a href=\"{$upgradeUrl}\">kliknite ovde</a> za nastavak.</p>\n"
"<p>Se stai aggiornando da una installazione OJS 2.x esistente, <a href=\""
"{$upgradeUrl}\">fai click qui</a> per procedere.</p>\n"
"<p>Pokud provádíte upgrade existující instalace OJS 2.x, <a href=\""
"{$upgradeUrl}\">Klikněte zde</a> pro pokračování.</p>\n"
"<p>Lehendik daukazun OJS 2.x bertsioa berritzera bazoaz, egin klik <a href=\"{$upgradeUrl}\">hemen</a>.</p>\n"
"<p>Wanneer u een upgrade doet van een bestaande installatie van OJS 2.x, <a href=\"{$upgradeUrl}\">klik hier</a> om verder te gaan.</p>\n"