Oracle%20High%20Availability

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Oracle High Availability

• Doug Smith
• dougs_at_ksu.edu
• CIS 764
• Fall Semester 2007

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Agenda

• Introduction
• Context
• System Quality Attributes
• Availability
• Oracle Real Application Clusters
• Oracle Data Guard
• Oracle Maximum Availability Architecture

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System Quality Attributes

• Sometimes called Non-functional Requirements.
• Clements, Bass, and Kazman classification
• Qualities of the system availability,
  modifiability, performance, security,
  testability, usability.
• Business qualities time to market, cost and
  benefit, projected system lifetime, legacy system
  integration, etc..
• Qualities of the architecture itself conceptual
  integrity, correctness and completeness,
  buildability, etc.
• Architect responsibilities
• Elicit requirements related to system quality
  attributes.
• Provide an architecture that can realize the
  desired system quality attributes.

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Availability

• Two ways to improve availability
• Avoid system failure
• Repair quickly

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Avoiding System Failure

• Common approach redundancy
• Design system with sufficient redundancy to allow
  continued operation when components fail.
• Example application tier
• Multiple load balanced servers
• Redundant load balancing appliances
• Redundant network switches, routers, etc. etc.
• Oracle approach Oracle Real Application Clusters

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Dealing with Disaster

• What if the data center is lost?
• Cantor Fitzgerald eSpeed, WTC North Tower, 9/11.
• Disaster recovery plan mirrored data center
• Cantor back online when bond market reopened 47
  hours later.
• Tools and processes needed to rapidly repair or
  recover systems to make them available again.
• Oracle tool Oracle Data Guard

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Oracle Real Application Clusters (RAC)

• Oracle RAC provides the ability to run an Oracle
  database across a set of clustered servers.
• Cluster strategy provides fault tolerance a
  cluster server can be lost without impacting the
  functionality of the system.
• Provides a horizontal scalability capability
  servers can be added to support additional users
  and load

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RAC Physical Architecture
Figure from HP InfiniBand solution for Oracle
RAC environments
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Application Partitioning

• Oracle marketing literature implies any
  application can be run unchanged on RAC and scale
  up by adding additional nodes to the cluster.
• However
• Oracle RAC uses a shared everything clustering
  strategy.
• Contention between nodes for data blocks will
  limit scalability content will become worse in
  some cases as nodes are added to the cluster.
• Application partitioning needed to reduce
  contention at the block level, and to reduce
  cross-instance data swapping.
• Oracle 10g provides work load management features
• Allows routing specific users or functions to
  specific nodes.

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Oracle Data Guard

• Oracle Data Guard is a set of services for
  maintaining one or more standby databases.
• Transactionally consistent copies
• Both physical and logical copies are supported.
• Data Guard Services
• Redo transport
• Log apply
• Role Transition
• Standby to primary
• Primary to standby

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Redo Logs Context
From Oracle Architectural Components
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Oracle Data Guard Services
Figure from Oracle Data Guard Concepts and
Administration, Oracle 10g Release 2
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Oracle Maximum Availability Architecture
Figure from Oracle Maximum Availability
Architecture
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References

• Software Architecture in Practice, Second Edition
  by Len Bass, Paul Clements, Rick Kazman. Addison
  Wesley Professional, 2003.
• Cantor Fitzgerald - Forty-Seven Hours, Edward
  Cone and Sean Gallagher. Baseline Magazine,
  http//www.baselinemag.com/article2/0,1540,819256,
  00.asp
• HP InfiniBand Solution for Oracle RAC
  Environments, http//h71019.www7.hp.com/ActiveAnsw
  ers/downloads/HPInfiniBandSolution_OracleRAC.pdf
• Oracle Architectural Concepts, http//www.oracle.c
  om/technology/tech/migration/isv/docs/OracleArchit
  ectureOverview.pdf
• Oracle Data Guard Concepts and Administration,
  Oracle 10g Release 2, http//download-west.oracle.
  com/docs/cd/B19306_01/server.102/b14239/toc.htm
• Oracle Maximum Availability Architecture,
  http//www.oracle.com/technology/deploy/availabili
  ty/htdocs/maa.htm