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What is DB2 HADR?

DB2® High Availability Disaster Recovery (HADR) uses database logs to replicate data from the primary database to the standby database. 

Non-logged operations are allowed on the primary database, but not replicated to the standby database. If you want non-logged operations, such as updates to the history file, to be reflected in the standby database, you must take extra steps to cause this to happen.
The following are examples of cases in which operations on the primary database are not replicated to the standby database:

  • Tables created with the NOT LOGGED INITIALLY option specified are not replicated. Attempts to access such tables after an HADR standby database takes over as the primary database will result in an error.
  • All logged LOB columns are replicated. Non-logged LOB columns are not replicated. However, the space for them will be allocated on the standby database using binary zeroes as the value for the column.
  • Updates to database configuration using the UPDATE DATABASE CONFIGURATION and UPDATE DATABASE MANAGER CONFIGURATION commands are not replicated.
  • Database configuration and database manager configuration parameters are not replicated.
  • For user-defined functions (UDFs), changes to objects external to the database (such as related objects and library files) are not replicated. They will need to be setup on the standby via other means.
  • The recovery history file (db2rhist.asc), and changes to it, are not automatically shipped from the primary database to the standby database.
 It replicates data in real time from a primary database to one or more standby databases. In case the primary database fails, a standby database takes over as the new primary.


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