we are currently using OJS 3.0.2.0 and we have encountered problems regarding declining submissions, e-mails are not send from OJS to authors and reviewers.
We are considering upgrade to the most recent version 3.1.1.4, but our computer assistance has doubts that something might go wrong with the current version and archive of our journal.
Would you be so kind and direct us to some guidelines for safe upgrade or additional instructions which we must consider when upgrading?
Key factor is backups. You should backup your files folder, OJS folder and the database. If things go wrong during the upgrade, you just need to go back to the backup versions.
We always do a sandbox upgrade test in a separate server. This means that I do a complete copy of our OJS and do a test upgrade to find out any possible errors. This is mentioned also in the guide above.