Question: What do
I do to know the number of cores on my Oracle server?
Answer: To know the number of
cores you need only look at the cpu_count parameter.
At install time, Oracle knows if the CPU has core
architectures and sets cpu_count to the number of cores.
SQL> show parameter cpu
The oracle kernel will
determine the number of CPUs on a system during startup.
However, some new processors (i.e. Intel) have dual cores,
where we have two CPU's on one chip, and they appear as two
processors when they only occupy one slot, while this is
good for software performance it can be hazardous to your
license, Oracle has stated that they will charge a CPU
license fee for the extra cores in multiple core CPUs.
Intel Hyper-threading
chips are an example of a single chip that appears to be two
CPU's to the Oracle kernel. On Intel-based Oracle
servers running Linux or Windows, the cpu_count is
set to double the number of physical CPUs when using the
hyper-threading setting of the OS or BIOS.
Why is cpu_count
important?
The Oracle
cpu_count is determined when you start Oracle. The
cpu_count affects the Oracle cost-based optimizer
through many calculated parameters that use cpu_count
as their basis and are considered every time that Oracle
creates an execution plan for a SQL statement. A
doubled setting for cpu_count can result in changes
to your explain plans when moving from a single to multiple
CPUs or when you increase the number of CPUs in your system.
A single-core hyperthreading CPU counts as one CPU for
licensing, a dual-core CPU counts as 2.
If you are licensed for diagnostic and tuning packs, you
can display the number of sockets, cores and CPU's with this
script:
-- ******************************************************
-- CPU data from dba_hist_osstat
-- ******************************************************
col c1 heading '#|CPUs' format 999
col c2 heading '#|CPU|Cores' format 999
col c3 heading '#|CPU|Sockets' format 999
select
(select max(value) from dba_hist_osstat
where stat_name = 'NUM_CPUS') c1,
(select max(value) from dba_hist_osstat
where stat_name = 'NUM_CPU_CORES') c2,
(select max(value) from dba_hist_osstat
where stat_name = 'NUM_CPU_SOCKETS') c3
from dual;
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