Core files are a common occurence with unix/linux servers when you have a buggy application. I've seen a lot of these over the years

Core files are a dump of the memory segment as the application dies. As such, core files are only really helpful if you are a developer working on figuring out what is going on with your application. For the most part, we don't need them.

So let's get rid of them to save diskspace! There are quick and easy ways to do this, but I am going to take this the slow way that confirms that you have what you are looking for.

find / -name "*core*" -exec file {} \;

That command willl find all files that have "core" in them. IIRC, most linux variants use a filename of "core.#####" and then run a "file" ommand on them.

The output from "file" for a core file should state something like "this is a core dump of"

At that point, simply "rm" the core file. "rm /usr/local/app/core/.1234"