Database Error after VPS memory adjustment

Don’t know if this downtime/error is related to this change or not. Recently moved a client’s site to a VPS due to increased site traffic. Today I received a notice that the site exceeded the memory allocation and it recommended allocating more memory. So I did. There was some indication of downtime due to this upgrade because the VPS has to reboot. It has been almost 4 hours since this upgrade and the site is still down with a “Error establishing a database connection” message. The site has sporadically come back online for small moments but at the current moment, I cannot connect to the site. I have a support ticket but have yet to get a response. Any ideas on what is going on?