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##            How to implement Oracle Instance Caging             ##
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Instance Caging allows to dynamically limit the amount of CPUs used by each database instance. This option is specifically thought for shared environments where the database administrator has to guarantee resources to all the instances running on the same hardware.

-- Enable Resource Manager:

ALTER SYSTEM SET RESOURCE_MANAGER_PLAN = 'REAL_TIME_PLAN';
--or
ALTER SYSTEM SET RESOURCE_MANAGER_PLAN = 'FORCE:REAL_TIME_PLAN';

FORCE option prevents that the scheduler window activates a different plan during the job execution.

For more info about Resource Manager visit ResourceManager Blog

-- Enable Instance Caging:
ALTER SYSTEM SET CPU_COUNT=4 SCOPE=BOTH SID='*';

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##                            Instance Caging Test                                 ##
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Hardware SUN 8 Cores 64 Threads

One test database capped to 16 CPU – 25% of total hardware capacity.

ALTER SYSTEM SET RESOURCE_MANAGER_PLAN = 'default_plan';
ALTER SYSTEM SET cpu_count=16 scope=both sid='*';

The load generator opens 70 sessions producing intensive CPU activity, which as shown by the reports below
do not exceed the 25% od the total server capacity (%Usr column).
 
   Core Utilization for Integer pipeline
Core,Int-pipe         %Usr       %Sys    %Usr+Sys
-------------        ------     ------    --------
     0,0              21.92      3.99     25.91
     0,1              24.58      2.08     26.66
     1,0              23.16      2.27     25.43
     1,1              24.06      2.64     26.71
     2,0              22.73      3.03     25.76
     2,1              23.47      3.02     26.49
     3,0              23.56      2.86     26.42
     3,1              24.71      2.87     27.58
     4,0              23.53      2.07     25.60
     4,1              24.87      2.92     26.79
     5,0              24.98      2.87     27.85
     5,1              24.76      3.81     28.57
     6,0              23.53      4.11     27.64
     6,1              23.99      3.14     27.13
     7,0              24.72      3.55     28.26
     7,1              22.62      3.59     26.21
-------------       ------      ------    ------
    Avg             22.36       3.05     25.41


If on the Wait Events is present "resmgr:cpu quantum", it means that Instance Caging throttled the amount of CPUs available to the system.

INST_ID        SID     SQL_ADDR                   EVENT                    WAIT_CLASS      STATE                 WAIT_MICRO    REMAING      TOT_TIME       LAST_WAIT
-------       ------  ----------------    ------------------------------ ---------------  ------------------     ----------    ----------   ----------     ----------
      1       676     000000047ECC5BD0     resmgr:cpu quantum             Scheduler       WAITED KNOWN TIME       11599           11599         43834
      2       624     000000047D7D38D0     resmgr:cpu quantum             Scheduler       WAITED KNOWN TIME       11599           11599         43834
      2       395     000000047BCA97A8     resmgr:cpu quantum             Scheduler       WAITING                 11669              -1         11668          0
      1       300     000000047C8D6B38     resmgr:cpu quantum             Scheduler       WAITED KNOWN TIME       11677           11677           589
      2       317     00                   resmgr:cpu quantum             Scheduler       WAITED KNOWN TIME       11677           11677           589
      1       649     000000047ECC5BD0     resmgr:cpu quantum             Scheduler       WAITING                 14445              -1         14444          0
      2       676     000000047D7D38D0     resmgr:cpu quantum             Scheduler       WAITING                 14445              -1         14444          0
      1       148     000000047C8D6B38     resmgr:cpu quantum             Scheduler       WAITING                 14827              -1         14826          0
      2      1413     000000047D7D36E0     resmgr:cpu quantum             Scheduler       WAITED KNOWN TIME       18824           18824         98023
      1       148     000000047ECC4010     resmgr:cpu quantum             Scheduler       WAITED KNOWN TIME       18824           18824         98023
      1       149     000000047C8D6B38     resmgr:cpu quantum             Scheduler       WAITING                 19122              -1         19121          0
      1        69     000000047C8D6B38     resmgr:cpu quantum             Scheduler       WAITING                 19177              -1         19176          0
      2        51     000000047BCA97A8     resmgr:cpu quantum             Scheduler       WAITING                 19177              -1         19176          0
      2      1106     000000047BCA97A8     PX Deq: Signal ACK RSG         Other           WAITING                 112660           7340        120000          0