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DB2 HADR and HADR_PEER_WINDOW settings

23 August,2011 by Tom Collins

Setting HADR_PEER_WINDOW at zero ,  only blocks primary transactions for the time specified in HADR_TIMEOUT.   

If the HADR_PEER_WINDOW is set to greater than zero, then the Primary database waits until the connection is restored  or the HADR_PEER_WINDOW  period finishes.

 Connections between the Primary and Standby databases are temporarily broken .

Possible reasons can be:

a) network 

b) OS issues

c) DB2 problems. How to report a DB2 performance problem

Leaving the HADR_PEER_WINDOW at zero , is beneficial to maintain availability.   At zero, soon as the connection between Primary and Standby  closes , the Primary is no longer in Peer state. 

 Therefore ,

a)  For data consistency , go for a non-zero value

b)  For data availability , consider a zero value

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Author: Rambler(http://www.dba-db2.com)

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Posted by Tom Collins at 9:47 AM in High Availability | Permalink | Comments (2) | TrackBack (0)

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What are the majority of installations doing with this (new) parm? I realize the tradeoffs, and each site has different requirements. The default is zero (perhaps for compatibility, who knows), but the IBM recommendation is "A recommended minimum value is 120 seconds." (V10.5 Info Center)

Posted by: George Peters | Apr 2, 2014 3:57:59 PM

IBM recommend 120 second - to maximise data consistency.
To find the optimal number of seconds , run some tests on your systems and monitor the time it takes to reconnect

Posted by: Jack Vamvas | Apr 18, 2014 12:08:45 AM

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