So the reason I posted under Drupal is because the Drupal installation was throwing an opcache error. These technologies and systems are interconnected so this is in the interest of some Drupal users even though opcache may be a external technology. Drupal doesn't exist in a vacuum, I wish it did because it would probably be easier to manage.
Here is what I found, in case anybody else is having this issue (disclaimer: I'm not an expert on this item... just sharing what I found). I don't know how to put the opcache in memory/database, as suggested (sounds like a good idea) and my host, and Drupal error message, seemed to be wanting a location for this cache, so that's how I proceeded.
Due to some word choices in the directions I found (by host and Drupal), I was under the impression that the cache might be specific for each site (I'm running a multi-site shared code base Drupal install) But the cache seems to be just for any php on the system, so I put the opcache folder under the 'sites' folder in the Drupal directory structure and pointed to it there in my php.ini. So Drupal built a cache folder in there, with a very long number string name. The PHP status information, from the Drupal Status page, will indicate if the opcache is enabled and it's perimeters.
Another problem I had was, when a new cache was built the old ones lingered and ate up a file number limit I had. It seems to be safe to delete these opcache entries and free up space (a lot of space). The caches will rebuild with the current date. So it's safe to play around with this, this is just a cache of PHP code so the server doesn't have to re-run it each time (for efficiency). This (opcache) seems to be new for D8+, I don't recall this issue for prior Drupal versions.
I think it's important to remember that everybody situation is different and there is a reason people reach out for help here. The setup that works for some may not be the case for someone else, and these technologies and networks are getting more and more bloated, complex and tangly. I hope someone may find this useful if they happen to have a similar problem and find themselves here. Thanks for the replies!