September 21, 2011 at 8:51 am
L' Eomot Inversé (9/21/2011)
(which I believe is that replication continues as normal but with reduced replication latency - but I can't find a reference to back that up).
I guess we need to test this scenario 🙂
M&M
September 21, 2011 at 9:49 am
Thanks for the question. Replication is a weak area for me so I had to guess and guessed wrong.
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September 21, 2011 at 12:54 pm
Learned something new today. I missed the question because it was a little unclear I think.
http://brittcluff.blogspot.com/
September 21, 2011 at 7:47 pm
Thanks for the question. Replication and mirroring are topics I need to read up on more.
September 22, 2011 at 12:58 am
mohammed moinudheen (9/21/2011)
L' Eomot Inversé (9/21/2011)
(which I believe is that replication continues as normal but with reduced replication latency - but I can't find a reference to back that up).
I guess we need to test this scenario 🙂
Test away. I came accross this when I needed to take application consistant snapshots of my mirror server databases every 30 minutes for reporting purposes (Using NetApp SnapDrive article will be coming soon). What I found was that replication latency increased at during time the mirror was "suspended" or "paused". After a bit of research i found out that because the transactions where not "hardened" in the log that the replication log reader agent would not replicate the transactions. As this caused us quite a few issues as we have external facing customer websites accessing the subscriber databases a decision was made to enable trace flag 1448.
http://support.microsoft.com/kb/937041
For those who are still not sure on the details of the correct answer, see the cause section of the above link.
Thanks
Chris
September 22, 2011 at 12:59 am
anthony.green (9/21/2011)
Good question ChrisAnt
Thanks Ant, appreciate it.
September 22, 2011 at 2:24 am
chris.mcgowan (9/22/2011)
... As this caused us quite a few issues as we have external facing customer websites accessing the subscriber databases a decision was made to enable trace flag 1448.http://support.microsoft.com/kb/937041
For those who are still not sure on the details of the correct answer, see the cause section of the above link.
Thanks
Chris
So the correct answer once more is: It depends.
If you have trace flag 1448 enabled, transaction replication is not affected. If it's not, no transactions of the exposed publisher are replicated to the mirror. :Whistling:
Regards,
Michael
September 22, 2011 at 5:06 pm
chris.mcgowan (9/22/2011)
mohammed moinudheen (9/21/2011)
L' Eomot Inversé (9/21/2011)
(which I believe is that replication continues as normal but with reduced replication latency - but I can't find a reference to back that up).
I guess we need to test this scenario 🙂
Test away. I came accross this when I needed to take application consistant snapshots of my mirror server databases every 30 minutes for reporting purposes (Using NetApp SnapDrive article will be coming soon). What I found was that replication latency increased at during time the mirror was "suspended" or "paused". After a bit of research i found out that because the transactions where not "hardened" in the log that the replication log reader agent would not replicate the transactions. As this caused us quite a few issues as we have external facing customer websites accessing the subscriber databases a decision was made to enable trace flag 1448.
http://support.microsoft.com/kb/937041
For those who are still not sure on the details of the correct answer, see the cause section of the above link.
Thanks
Chris
Are you sure that you were running mirroring in High-safety mode with automatic failover?
According to the BoL page on Replication and Database Mirroring (and corresponding pages for earlier SQL Server versions) if the mirror is unavailable in that mode the log reader continues to send commands to the distributor, so it's clear that it doesn't wait for the log records to be hardened to the mirror. It's high performance where the behaviour you describe is encountered, according to the documentation (in high safety mode without automatic failure no activity is permitted in the master when the mirror is inaccessible, and I imagine that includes when mirroring is paused).
Tom
September 23, 2011 at 1:06 am
Nice question, thanks.
Need an answer? No, you need a question
My blog at https://sqlkover.com.
MCSE Business Intelligence - Microsoft Data Platform MVP
September 23, 2011 at 1:29 am
L' Eomot Inversé (9/22/2011)Are you sure that you were running mirroring in High-safety mode with automatic failover?
According to the BoL page on Replication and Database Mirroring (and corresponding pages for earlier SQL Server versions) if the mirror is unavailable in that mode the log reader continues to send commands to the distributor, so it's clear that it doesn't wait for the log records to be hardened to the mirror. It's high performance where the behaviour you describe is encountered, according to the documentation (in high safety mode without automatic failure no activity is permitted in the master when the mirror is inaccessible, and I imagine that includes when mirroring is paused).
That would have been my understanding as well, but haven't received any feedback to my post two days ago.
Thanks,
Michael
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