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Our 11g RAC cluster has two nodes, each with 8 CPU cores and a memory target of 16GB. System RAM is 64GB (don't ask me why the memory target is just 16GB, I wasn't there when that choice was made). The disk is SSD. The CPU load as shown in the Enterprise Manager never exceeds 25% and is usually around 20%, and the RAM occupancy stays around 20%. The IO operations per second (that worry my the most) vary between 2000 and 8000, with an average around 5500. The load is mostly OLTP style. System load is around 1, maybe 1.5.

My question is, can we consider this cluster to be "heavily" loaded? Again my concern is with IO, obviously CPU and RAM are not stressed.

I'm asking because the application occasionally shows signs of sluggishness. The developers refuse to put logging statements that would show how much time a query takes to run ("too many queries"), so I'm left looking for less direct ways to figure this out.

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  • Do you have baseline benchmark results of the underlying disk subsystem? (Eg Oracle's ORION) – Michael Kutz Feb 2 '19 at 1:00
  • A single piece of entry level consumer SATA3 SSD can do about 90000+ IOPS. Your system can run with 2000-8000 IOPS, which is far below. You have 8 CPU cores and a load of 1-1,5. You have 64 GB RAM and you use 20% of it. No, that system is not heavily loaded. If your concern is with IO, measure it. If the application is slow, focus on that and SQLs it executes. It is so typical, when an application is slow and DBAs start looking into hardware resources, before even trying to analyze the database with SQLs itself. You have the most direct tool for measuring SQL statements, called SQL tracing. – Balazs Papp Feb 2 '19 at 10:18
  • @Michael I've never heard of Oracle's ORION. – GID Feb 2 '19 at 12:15
  • @BalazsPapp Are the Oracle EM IOPS and the published SSD IOPS the same and therefore comparable? How can I use SQL tracing to better understand what's going on? I have zero DBA training, I learn on the job, and I do much more than DB admin, small companies can't afford full-time DB admins, nor Oracle's training costs, unfortunately. – GID Feb 2 '19 at 12:18
  • ORION is an IO benchmark and configuration tool. The results can be used to confirm the exact % of IOPS and "data teansfer" that your ststem can handle. – Michael Kutz Feb 2 '19 at 12:30

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