Re: CPU WAIT in OEM (Light green area)

Hi Jack!

Vmstat is the wrong tool to measure CPU.  You should use sar or mpstat. I prefer "mpstat" because it's more modern and provides more data:

root_at_umajor:/home/mgogala# mpstat 3 3 Linux 5.3.0-24-generic (umajor)     11/17/2019 _x86_64_    (16 CPU)

08:13:40 PM  CPU    %usr   %nice    %sys %iowait %irq   %soft  %steal  
%guest  %gnice   %idle
08:13:43 PM  all    0.06    0.00    0.04    0.00 0.00    0.00    0.00    
0.00    0.00   99.90
08:13:46 PM  all    0.15    0.00    0.25    0.00 0.00    0.00    0.00    
0.00    0.00   99.60
08:13:49 PM  all    0.04    0.00    0.06    0.00 0.00    0.00    0.00    
0.00    0.00   99.90

08:16:18 PM     all      0.10      0.00      0.08 0.00      0.00     99.81
08:16:21 PM     all      0.33      0.00      0.17 0.00      0.00     99.50
08:16:24 PM     all      0.06      0.00      0.02 0.00      0.00     99.92

[root_at_ora122 sa]# sar -u -f sa24
Linux 4.14.35-1902.4.8.el7uek.x86_64 (ora122) 08/24/2019     _x86_64_    (3 CPU) 10:53:20 AM       LINUX RESTART 11:00:01 AM     CPU     %user     %nice   %system %iowait    %steal     %idle

11:10:01 AM     all      3.26      0.00      0.41 0.65      0.00     95.69
11:20:01 AM     all      0.85      0.00      0.26 0.17      0.00     98.72
11:30:01 AM     all      0.27      0.22      1.17 0.16      0.00     98.19
11:40:01 AM     all      0.21      0.00      0.20 0.08      0.00     99.51
11:50:01 AM     all      0.80      0.00      0.22 0.11      0.00     98.87

12:34:10 PM       LINUX RESTART 12:40:01 PM     CPU     %user     %nice   %system %iowait    %steal     %idle
12:50:01 PM     all      0.24      0.00      0.16 0.09      0.00     99.51 01:00:01 PM     all      2.31      0.00      0.34 0.22      0.00     97.12 Average:        all      1.27      0.00      0.25 0.15      0.00     98.32 [root_at_ora122 sa]#

Snapshots are taken 10 minutes apart and usually go up to a month back. I am using virtual machines which can be inactive for several days. Other than that, you can see CPU Wait event if you are using DBMS_RESOURCE_MANAGER. However, if uptime and other tools, show that the CPU is not much used, then don't pay any attention to that event.

Regards

On 11/17/19 7:53 PM, Jack van Zanen wrote:
> Hi All
>
>
> I am seeing on occasion that CPU WAIT in OEM graph gets very prominent
> According to
> "https://blog.orapub.com/20150210/what-is-light-green-oracle-database-cpu-wait-time.html"
> The CPU WAIT is when Oracle is waiting to get on CPU (in the queue)
>
> I would however expect to see CPU pressure when this happens
>
> however on OS CPU have lots of IDLE time
>
> [oracle_at_cltsadm01vm01 AWR]$ vmstat 10 10
> procs -----------memory---------- ---swap-- -----io---- --system--
> -----cpu-----
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in cs us sy
> id wa st
> 13  0      0 91456296 1246408 72531584    0    0     8    32  0    0
> 22  4 74  0  0
>  9  0      0 91441104 1246408 72532288    0    0     0   188 50024
> 41230 28  3 69  0  0
> 13  0      0 91481680 1246408 72533216    0    0     1   266 48898
> 41615 28  3 69  0  0
>  9  0      0 91487496 1246408 72536520    0    0     0   242 60376
> 46185 26  3 71  0  0
> 10  0      0 91501456 1246408 72537696    0    0     1   196 45629
> 37927 24  5 71  0  0
> 12  0      0 91464880 1246412 72541536    0    0     0   252 46247
> 39331 29  4 67  0  0
>
>
>
>
> Jack van Zanen
>
>
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-- 
Mladen Gogala
Database Consultant
Tel: (347) 321-1217


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