HADR - AIX

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  • agentlease@hotmail.com
    #1

    HADR - AIX

    Hi,

    If the HADR state is 'Disconnected' and commit transactions to the
    Primary database, in the event of a Failover to the Standby database,
    how do we determine if it is safe i.e. how do we know how far behind
    the standby database is?

    Basically what is the procedure to determine if it's safe to do a
    failover to the standby with a takeover hadr .....force.
    Tags: None
    • Mark A
      #2
      Re: HADR - AIX

      <agentlease@hot mail.comwrote in message
      news:0481bdf8-eb8a-4453-9235-e294c03c17e7@x1 6g2000prn.googl egroups.com...
      Hi,
      >
      If the HADR state is 'Disconnected' and commit transactions to the
      Primary database, in the event of a Failover to the Standby database,
      how do we determine if it is safe i.e. how do we know how far behind
      the standby database is?
      >
      Basically what is the procedure to determine if it's safe to do a
      failover to the standby with a takeover hadr .....force.
      It is only safe to do a takeover by force if the primary server is not
      available to the application (crashed, network connection is not accessible,
      etc). If you are automating the takeover with a Cluster Manager, then make
      sure your instance is not on autostart.

      You can run a command on the primary and standby to see where the log
      position is. Normally if they are in peer state you can run it from either
      server, but if in disconnected state you would have run it on each server to
      get the log position of each. You have two choices:

      db2 get snapshot for database on <dbname(there is section on HADR in the
      output)
      db2pd -d <dbname-hadr


        Comment

        • Steve Pearson (news only)
          #3
          Re: HADR - AIX

          You may also want to look at the HADR Peer Window feature, which can
          help ensure that transactions do not commit on the primary without
          replication to the standby, for a configurable period of time. This
          is useful where there is a high desire for consistency at failover,
          and esp. where failover is automated. Note that this choice for
          consistency does trade off against availability, as when the HADR pair
          is disconnected, the primary (in SYNC or NEARSYNC modes) cannot commit
          transactions during Peer state, nor in the new Disconnected Peer state
          that comes with the Peer Window feature.

          Some intro material here:

          http://publib.boulder.ibm.com/infocenter/db2luw/v9r5/index.jsp?topic=/com.ibm.db2.luw.wn.doc/doc/c0051997.html


          Regards,
          - Steve P.
          --
          Steve Pearson, DB2 for Linux, UNIX, and Windows, IBM Software Group
          "Portland" Development Team, IBM Beaverton Lab, Beaverton, OR, USA

            Comment

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