Call now: 252-767-6166  
Oracle Training Oracle Support Development Oracle Apps

 
 Home
 E-mail Us
 Oracle Articles
New Oracle Articles


 Oracle Training
 Oracle Tips

 Oracle Forum
 Class Catalog


 Remote DBA
 Oracle Tuning
 Emergency 911
 RAC Support
 Apps Support
 Analysis
 Design
 Implementation
 Oracle Support


 SQL Tuning
 Security

 Oracle UNIX
 Oracle Linux
 Monitoring
 Remote s
upport
 Remote plans
 Remote
services
 Application Server

 Applications
 Oracle Forms
 Oracle Portal
 App Upgrades
 SQL Server
 Oracle Concepts
 Software Support

 Remote S
upport  
 Development  

 Implementation


 Consulting Staff
 Consulting Prices
 Help Wanted!

 


 Oracle Posters
 Oracle Books

 Oracle Scripts
 Ion
 Excel-DB  

Don Burleson Blog 


 

 

 


 

 

 
 

Oracle Instance Caging tips

Oracle Database Tips by Donald BurlesonSeptember 6,  2015

Oracle instance caging in Oracle Database Resource Manager

Oracle notes that their Oracle Instance Caging utility is used in consolidated shops where many instances share the same server CPU resources.  Due to falling prices on large servers with 32 and 64 CPU's shops all across America are undertaking.  However, there is a fundamental argument about instance consolidation and the fencing (caging) if CPU resources:

  • No caging:  There is no better way for the sharing of computer resources than to have them directly available to all instances on the server.  If one instance "hogs" the CPU's, it is easy to add more processors.

Caging:  One instance might have a "rogue" task that hogs all of the CPU, adversely affecting not only that instance, but other instances on the server.

Expert Tip:  Having used both approaches, I do not recommend using instance caging because while there is this layer of protecting against "hogging", this is a small risk, and it is more than outweighed by the ability to share computing resources between instances, especially when some instances are idle and others are performing computationally intensive tasks..

Oracle Server Consolidation

, moving dozens and hundreds of instances into a single server for easier management and resource sharing.

Similar to "fencing" tools from the 1980's mainframes (e.g. the Prism tool), Oracle instance caging runs inside the database resource manager (DRM) and is related with RAC One Node to facilitate super fast instance relocation is cases of server failure.

The Oracle docs note that instance caging is like CPU fencing, dedicating processors to specific instances, a way to prevent one instance from "hogging" the processors:

Instance caging is a method that uses an initialization parameter to limit the number of CPUs that an instance can use simultaneously.

In the previous example, if you use instance caging to limit the number of CPUs to four for each of the four instances, there is less likelihood that one instance can interfere with the others.

There are also several new dictionary views relating to instance caging.  The dba_rsrc_plans offers several out-of-the-box resource plans, the v$rsrc_consumer_group, dba_rsrc_plans, and v$rsrcmgrmetric_history.

select
   plan
from
   dba_rsrc_plans;


PLAN
------------------------------
DEFAULT_PLAN
INTERNAL_QUIESCE
INTERNAL_PLAN
APPQOS_PLAN
DEFAULT_MAINTENANCE_PLAN
ETL_CRITICAL_PLAN
MIXED_WORKLOAD_PLAN
ORA$AUTOTASK_SUB_PLAN
ORA$AUTOTASK_HIGH_SUB_PLAN
DSS_PLAN

There is also the

select
   name,
   consumed_cpu_time,
   cpu_wait_time
from
   v$rsrc_consumer_group;

select
   begin_time,
   consumer_group_name,
   cpu_consumed_time,
   cpu_wait_time
from
   v$rsrcmgrmetric_history
order by
   begin_time;

Oracle instance caging appears to be identical in  function to these approaches for dedicating CPU to instances in a monolithic server environment.  There are many alternatives to resource caging:

Oracle says that these steps are required to enable instance caging for each instance:
  1. Enable the Resource Manager by assigning a resource plan, and ensure that the resource plan has CPU directives, using the mgmt_p1 through mgmt_p8 parameters.

    See "Enabling Oracle Database Resource Manager and Switching Plans" for instructions.

  2. Set the cpu_count initialization parameter.

    This is a dynamic parameter, and can be set with the following statement:

    ALTER SYSTEM SET CPU_COUNT = 4;


How to deploy instance caging

While CPU fencing tools have been around for decades, tools such as Vmware also allow for CPU and RAM fencing.  However, fencing with instance caching can be wasteful (since other instances may not share the CPU), and it's quite rare for one Oracle instance to "hog" an entire bank of processors.

Remember, the goal of server consolidation is to facilitate sharing of processor resources, not hinder it with instance caging.  Hence, I do NOT recommend deploying instance caging without careful testing and justification.

See these important related notes for Oracle instance caging:

 

 

��  
 
 
Oracle Training at Sea
 
 
 
 
oracle dba poster
 

 
Follow us on Twitter 
 
Oracle performance tuning software 
 
Oracle Linux poster
 
 
 

 

Burleson is the American Team

Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

Verify experience! Anyone considering using the services of an Oracle support expert should independently investigate their credentials and experience, and not rely on advertisements and self-proclaimed expertise. All legitimate Oracle experts publish their Oracle qualifications.

Errata?  Oracle technology is changing and we strive to update our BC Oracle support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:  

and include the URL for the page.


                    









Burleson Consulting

The Oracle of Database Support

Oracle Performance Tuning

Remote DBA Services


 

Copyright © 1996 -  2017

All rights reserved by Burleson

Oracle ® is the registered trademark of Oracle Corporation.

Remote Emergency Support provided by Conversational