PEM database server is restarted during PEM server upgrade, and that would require a downtime. Below are the high-level steps:
1) Upgrade the remote PEM agents first
2) Upgrade PEM server (using pem-server installer, Database option)
3) Upgrade Apache ( using pem-server installer, Web services option)
We also recommend you to upgrade to the latest version of PEM server which 7.5 as it has more new and exciting features.
Please refer below documentation for the details
Please let us know in case of any issues/queries.