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Old 07-30-2007, 02:59 AM   #1
Registered: Oct 2006
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How to monitor system

Iīve a system running Oracle IAS. I see that %sys is greater that used %user when I do a iostat.

I suppose that itīs a problem of memory. So if I increase the amount of memory the %sys will decrease, but Iīm not sure. Oracle IAS allways uses all memory of the system so Mem: parameters have to be read carefully.

How can i be sure that the problem is due to lack of memory and that increasing memory will decrease %system. I donīt want to buy the memory if not necesary.

At this moment, pararamteres ar low due to there are few users, but they use to be greater.


09:47:11 up 24 days, 44 min, 1 user, load average: 0,92, 1,10, 1,07
480 processes: 477 sleeping, 2 running, 1 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 9,7% 0,0% 20,5% 0,0% 0,2% 1,5% 67,9%
cpu00 5,9% 0,0% 12,8% 0,0% 0,7% 1,9% 78,4%
cpu01 9,6% 0,0% 21,9% 0,0% 0,0% 1,1% 67,1%
cpu02 9,0% 0,0% 14,8% 0,0% 0,0% 1,5% 74,5%
cpu03 14,3% 0,0% 32,5% 0,0% 0,1% 1,3% 51,4%
Mem: 2061652k av, 2031420k used, 30232k free, 0k shrd, 2624k buff
1351456k actv, 51556k in_d, 30884k in_c
Swap: 2044072k av, 508372k used, 1535700k free 287432k cached
Old 07-31-2007, 04:18 PM   #2
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You say there is a problem but looking at your iostat figures I don't see any problem. The only thing that catches my attention is the number of processes. (480) But I haven't run Oracle so I don't know if that is expected or not.

Your overall workload hovers around 1.0 but since you have 4 CPUs the theoretical full workload would be 4.0. So it looks like you could quadruple the CPU workload without straining the operating system.

All of your CPUs spend most of their time idling.

You are using 500 MB of your swap file. Your total swap file size is 2 GB. No problem there.

The RAM figures are pretty typical of Linux. You say that Oracle uses all available RAM. Linux does the same thing with or without Oracle. No problem there.

The iowait for each CPU is less than 2%. No problem there.

The system CPU time is less than 33% for each CPU. No problem there.

The user CPU time is less than 15% for each CPU. No problem there. The ratio of user time to system time is irrelevant. That is determined by your workload. There is no right or wrong. You just have to figure what you should expect to see for a given workload and compare that to what you actually see. In this case the fact that the system spends twice as much time in system mode as in user mode does not indicate a problem. Remember that a database server is going to spend a lot of time managing locks and data accesses, both of which are CPU intensive.

I really don't think that you have a problem. If you want to add more work to the system then the only area that you might want to change is to add RAM. I say that because you are already swapping under the current workload. Otherwise the CPU and the i/o are ready to do more work than you currently give them.
Old 08-01-2007, 01:40 AM   #3
Registered: Oct 2006
Posts: 295

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Thanks for your answer. Itīs what I was looking for. Iīll go on monitoring system and watching specially (as you have told me) the iowait parameter.

The number of process is normal because Oracle IAS open hundreds of process to increase the speed.




iostat, memory, monitor

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