This document discusses high availability options for DB2 data centers, including PowerHA SystemMirror, DB2 HADR, and InfoSphere Data Replication. PowerHA provides failover clustering through separate hardware and shared storage. DB2 HADR uses log shipping for continuous backup and fast takeover. InfoSphere replicates transactions to remote sites for no single point of failure. While each option has advantages, combining methods provides better risk coverage, though too much complexity can introduce failures. Thorough testing is important.

1. © 2015 IBM Corporation
High Availability Options for
DB2 Data Centre
Zoran Kulina
IBM Global Services

2. © 2015 IBM Corporation2
Table of contents
1. What is High Availability?
2. PowerHA SystemMirror
3. DB2 HADR feature
4. InfoSphere Data Replication
5. Conclusion
High Availability Options for DB2 Data Centre

3. © 2015 IBM Corporation3
What is High Availability?
Availability
Degree to which a database is available to users.
Top priority for mission critical systems (e.g., air traffic control).
Ideally close to 100% for critical databases or tables.
Unavailability results in lost revenue, shaken customer loyalty and damaged reputation.
High Availability Options for DB2 Data Centre
Source: http://www.evolven.com/blog/downtime-outages-and-failures-understanding-their-true-costs.html

4. © 2015 IBM Corporation4
What is High Availability?
High Availability
Set of components and procedures for ensuring that a database system remains
operational and accessible during planned or unplanned outages.
Real-time database monitoring and failure detection.
Fast and automated recovery.
Transparent to end users.
Not a specific technology.
Not a quantifiable attribute.
Not a synonym for uptime.
High Availability Options for DB2 Data Centre

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What is High Availability?
Characteristics of a High Availability solution
Incorporates redundancy across most or all components.
Protects from hardware and software failures, human errors, data corruptions and site
disasters.
Delivers near zero downtime from availability perspective.
Detects errors and outages in timely fashion.
Recovers from outages as quickly as possible.
Facilitates transparent recovery and workload swap.
Provides a reliable failover mechanism.
Eliminates or minimizes planned downtime.
Offers consistent performance on each node.
High Availability Options for DB2 Data Centre

6. © 2015 IBM Corporation6
PowerHA SystemMirror
Characteristics
Failover clustering methodology
Separate hardware and software
Shared instance and database storage
Advantages
Proven technology
Cost effective
Disadvantages
Database a single point of failure
Requires specialized storage
Increased administrative overhead
Servers must be in close physical proximity (SAN latency)
High Availability Options for DB2 Data Centre
Source: High Availability and Disaster Recovery Options for DB2 for LUW (IBM Redbook SG24-7363-02)

7. © 2015 IBM Corporation7
DB2 HADR feature
Characteristics
Log shipping methodology
Continuous “backup and restore”
Separate instances and databases
Advantages
No single point of failure
Extremely fast takeover
Easy to implement and maintain
Disadvantages
No built-in automatic takeover
Uses more hardware resources
Some potential for data inconsistency
High Availability Options for DB2 Data Centre
Source: http://www.ibm.com/developerworks/data/library/long/dm-1206hadrmultiplestandby

8. © 2015 IBM Corporation8
InfoSphere Data Replication
Characteristics
SQL replication methodology
Transactions re-executed at remote site
Covers all or subset of tables
Advantages
No single point of failure
Extremely fast failover
Used for purposes other than HA
Disadvantages
Uses more hardware resources
Complex configuration and maintenance
More ways for things to go wrong than in other solutions
High Availability Options for DB2 Data Centre
Source: http://www.ibm.com/developerworks/library/bd-infosphere-datarep/index.html

9. © 2015 IBM Corporation9
Conclusion
No one size fits all solution:
– PowerHA focused on hardware redundancy.
– HADR database disaster recovery oriented.
– Replication primarily concerned with data streaming.
Determine how to mitigate the drawbacks of each solution.
Combine multiple solutions for a better risk coverage.
Mind the law of diminishing returns:
– Too much complexity introduces more failure points.
Test thoroughly and often.
High Availability Options for DB2 Data Centre

10. © 2015 IBM Corporation10
References
Improving Systems Availability (IBM Global Services whitepaper)
http://www.dis.uniroma1.it/irl/docs/availabilitytutorial.pdf
High Availability and Disaster Recovery Options for DB2 for Linux, UNIX, and Windows (IBM
Redbook)
http://www.redbooks.ibm.com/abstracts/sg247363.html
Downtime, Outages and Failures - Understanding Their True Costs
http://www.evolven.com/blog/downtime-outages-and-failures-understanding-their-true-
costs.html
High Availability Options for DB2 Data Centre