Is it safe to delete dbcache.log file?

Yes.

You can and should delete the dbcache.log file if you find that file is to large. Just navigate to /public_html/wp-content/cache/log/000000/ folder and delete the file (skip recycle bin).

If you wanted, you could also delete the other two files, minify.log and pagecache.log.

Do not worry, you will not break your WordPress website.