IDS Forum

Re: HDR and ER Running Together

Posted By: Madison Pruet
Date: Tuesday, 19 June 2012, at 11:46 a.m.

In Response To: Re: HDR and ER Running Together (Keith Simmons)

It will wait unless HDR has been flagged as off because of connection
timeouts.

The issue is that when an HDR failover in an async mode occurs, there c=
an
be transactions committed on the old primary. Those transactions can be=
come
'lost transactions' after failover. If ER were to transmit those
transactions, then the ER targets would have the transaction, but the H=
DR
pair on which it originated would not. That's why ER has to wait until=
it
knows that the transaction has made it to the HDR secondary.

If ER has a such a txn, it will attempt to force flush the HDR transmit=

buffers. If that can not be done because of a temporary network outage=
,
you will get the message that you saw.

From: "Keith Simmons" <smiley73@gmail.com>
To: ids@iiug.org,
Date: 06/19/2012 07:44 AM
Subject: Re: HDR and ER Running Together [27388]
Sent by: ids-bounces@iiug.org

Thanks Madison,

So am I correct in thinking that while HDR is stopped for any reason
ER will also pause, regardless of whether HDR is in synchronous or
asynchronous mode ?

I'm trying to get my head around the implications of this.

We use the target(s) of the ER as part of our monitoring and feed-
back system and also as a read-only access for some customer
facing web-pages to allow them to track orders in 'almost' real time.

It would seem that if either the HDR Secondary or HDR Primary fail
for any reason and require an extended portion of down-time (but
not long enough to cycle the logs and require a complete re-
instantiation of HDR) then we will not be able to maintain these
targets in step. The alternative I think, therefore, is, during any fai=
lure

likely to take more than 3-4 hours to resolve, to switch the remaining
HDR server to stand- alone and then restart HDR using an archive/
restore (not ideal for a 1Tb instance on each end of a 100 mile WAN
link).

Please can you confirm this reasoning and conclusion.

Keith

On 19 June 2012 13:38, Madison Pruet <mpruet@us.ibm.com> wrote:
> If a replicated transaction is replicated via ER prior to ER knowing =
th=3D
> at
> it has made it to the HDR secondary, then there would be inconsistenc=
y =3D
> in
> the event of a failover. So we don't allow ER to replicate the transa=
c=3D
> tion
> until we know that the secondary has the transaction.
>
> From: "Keith Simmons" <smiley73@gmail.com>
> To: ids@iiug.org,
> Date: 06/19/2012 02:58 AM
> Subject: HDR and ER Running Together [27383]
> Sent by: ids-bounces@iiug.org
>
> Lets try again, this may be easier to read !!
>
> Set up is as follows:
>
> IDS 9.4 on AIX 5.3 --> ER over LAN --> IDS 10 on Solaris 2.8
> | |->
> IDS 11 on Solaris 2.10
> V
> Sync HDR over WAN
> |
> V
> IDS 9.4 on AIX 5.3
>
> Note ER is Primary to Secondary (one way).
>
> With this setup I am seeing lines in the error log of the HDR/ER
> Primary as follows:
> ER can not send replicated transactions due to HDR hang
> ER resume transmission of ER/HDR replicated transactions
> Also a few days ago the HDR secondary lost contact with the primary
> and couldn't automatically re-establish (brief network glitch). I sto=
pp=3D
> ed
> and restarted the secondary and this HDR re-established, but while
> HDR was not running (and until the logs had shipped and applied up
> to date) ER was frozen.
> I am trying to understand why ER keeps stopping (albeit briefly) and
> will not run while HDR is not connected. My suspicion is that it is r=
el=3D
> ated
>
> to the fact I have HDR in Synchronous mode but would like this
> confirmed. Also, if this is the case, is it possible to switch betwee=
n
> Synchronous and Asynchronous modes without restarting instances ?
>
> Many Thanks in anticipation
>
> Keith
>
> *********************************************************************=
**=3D
> ********
>
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
> =3D
>
>
>
***********************************************************************=
********

> Forum Note: Use "Reply" to post a response in the discussion forum.
>

***********************************************************************=
********

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=

Messages In This Thread

• HDR and ER Running Together
  Keith Simmons -- Tuesday, 19 June 2012, at 4:58 a.m.
  • Re: HDR and ER Running Together
    Madison Pruet -- Tuesday, 19 June 2012, at 8:38 a.m.
    • Re: HDR and ER Running Together
      Keith Simmons -- Tuesday, 19 June 2012, at 9:42 a.m.
      • Re: HDR and ER Running Together
        Art Kagel -- Tuesday, 19 June 2012, at 9:53 a.m.
        • Re: HDR and ER Running Together
          Keith Simmons -- Tuesday, 19 June 2012, at 10:02 a.m.
          • Re: HDR and ER Running Together
            Art Kagel -- Tuesday, 19 June 2012, at 10:19 a.m.
            • Re: HDR and ER Running Together
              Madison Pruet -- Tuesday, 19 June 2012, at 12:10 p.m.
              • Re: HDR and ER Running Together
                Keith Simmons -- Wednesday, 20 June 2012, at 4:43 a.m.
                • Re: HDR and ER Running Together
                  JACQUES RENAUT -- Wednesday, 20 June 2012, at 8:58 a.m.
                  • Re: HDR and ER Running Together
                    Keith Simmons -- Monday, 27 August 2012, at 8:50 a.m.
                    • Re: HDR and ER Running Together
                      JACQUES RENAUT -- Monday, 27 August 2012, at 11:01 a.m.
      • Re: HDR and ER Running Together
        Madison Pruet -- Tuesday, 19 June 2012, at 11:46 a.m.

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