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Find Oracle server excess capacity

Oracle Database Tips by Donald BurlesonJune 27, 2016

Question: What do I do to find the excess capacity of an Oracle server?  I want to do instance consolidation and I need to know how many instances I can fit onto a single server.  What is the procedure for determining the excess capacity for an Oracle server?

Answer:  To get the excess capacity for any Oracle server, you must get these three sets of values:

  • Server Maximum Capacity:  To know this, you must get the server type and model number and then look-up the maximum CPU and RAM capacity for that specific server.  Most servers have extra slots for CPU and RAM, and it is important to know the maximum capacity.  It is also helpful to know the age of each server, because you may want to replace the most elderly servers during the consolidation effort.
  • Server Actual capacity:  You can use AWR to get this information. (See Appendix A below)
  • Server Excess Capacity:  You can use OS statistics to get this information. 

    You want to look at the maximum values.  You want to look at the CPU runqueue from vmstat.  This value should rarely exceed the CPU count, the minimum values for free memory and the maximum network time.

When this is subtracted from the server actual capacity, this will give you the excess capacity for each server, expressed in three values:
- Excess CPU capacity
- Excess RAM
- Excess Network bandwidth

Note:  You must be licensed to use the Oracle diagnostic pack to use this AWR information.

Appendix A:

-- ******************************************************
-- Actual CPU capacity 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 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;
prompt ******************************************************
prompt Get server RAM Size
prompt ******************************************************
col c1 heading 'Physical|Memory|MB' format 999,999,999
   max(value)/1024/1024 c1
   stat_name = 'PHYSICAL_MEMORY_BYTES';



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