Database Reference
In-Depth Information
The report continues by giving OS-level information about the CPU utilization (be aware that up to and including
version 11.1.0.6, the
Instance CPU
section provides only the percentage values and uses different labels):
Host CPU (CPUs: 8 Cores: 8 Sockets: 2)
~~~~~~~~ Load Average
Begin End User System Idle WIO WCPU
------- ------- ------- ------- ------- ------- --------
5.98 7.09 23.83 0.89 74.75 21.86
Instance CPU
~~~~~~~~~~~~ % Time (seconds)
-------- --------------
Host: Total time (s): 7,001.7
Host: Busy CPU time (s): 1,768.2
% of time Host is Busy:
25.3
Instance: Total CPU time (s): 1,739.9
% of Busy CPU used for Instance:
98.4
Instance: Total Database time (s): 6,500.3
%DB time waiting for CPU (Resource Mgr): 0.0
The purpose of the previous excerpt is twofold:
% of time Host
is Busy
value provides you the information you need. If it's low (as in this case), everything
is fine. If its value is high (close to 100%, provided the CPUs aren't using simultaneous
multithreading), the resource usage profile of the top 5 events, as well as all other statistics
about waits events, might be misleading. In fact, in the case of a CPU shortage, many statistics
might be artificially inflated. Hence, your first goal would be to find a method to reduce the
CPU utilization.
•
To check whether the host (not the database instance) is CPU bound. The
•
To determine whether the CPU utilization at the OS level is primarily due to the database
instance you are looking at. This is an essential piece of information when a server runs
several database instances or even other applications. The most important value to check,
which shows how much of the total CPU utilization is due to the database instance you are
looking at, is
% of Busy CPU used for Instance
. If you see values of less than 80-90%, it
means that other applications are using a non-negligible amount of CPU. For example, in the
previous excerpt, notice that almost all of the CPU utilization (98.4%) is due to this database
instance. This means there's nothing else using a lot of CPU on this server.
After the OS-level information about the CPU utilization, OS-level information about the memory utilization is
shown. With it, you can know how much memory is available on the host (8 GB) and what percentage is used for the
SGA and PGA of the database instance you are looking at (15.1%):
Memory Statistics Begin End
~~~~~~~~~~~~~~~~~ ------------ ------------
Host Mem (MB): 7,974.6
7,974.6
SGA use (MB): 1,019.4 1,019.4
PGA use (MB): 175.1 183.1
% Host Mem used for SGA+PGA: 15.0
15.1
