The CPU requirements for DNS on an OES 2 Linux server vary depending on whether you are serving a few static zones without caching or whether you are serving an enterprise DNS.
The memory of the server must be sufficient to accommodate the cache and zones loaded off disk. OES 2 Linux requires at least 512 MB RAM. The max-cache-size option can be used to limit the amount of memory used by the cache, at the expense of reducing cache hit rates and creating more DNS traffic. It is still a good practice to have enough memory to load all zones and cache data into the memory. However, the best way to determine this for a given installation is to watch the name server in operation. After a few weeks, the server process should reach a relatively stable size where entries are expiring from the cache as fast as they are being inserted. Ideally, the resource limits should be set higher than this stable size.