Usually, which is more important for DB2 system performance - CPU processing or I/O access?

Question:

Usually, which is more important for DB2 system performance - CPU processing or I/O access?I/O operations are usually most critical for DB2 performance (or any other database for that matter).

Answer:

I'm sorry but the answer is a firm It depends. Depending on various factors most MVS boxes run short on either CPU or I/O. These factors include workload time of day day of the week etc. A capacity planner could give you a better list but these are the things I've seen in the past.For example daytime is usually devoted to getting info into and out of the system using CICS. This usually involves many many short inquiries or updates. Generally in this case the CPU is most important as the many levels of caching can handle these requests.However once users go home the main use switches doing updates to handling those updates. A single update I/O during the day can drive many thousands of I/O's to process that update. As batch processes work with whole filesets cache hit rates go down and I/O becomes more important.If you could provide more specifics perhaps we could come up with a better answer.