We have a SQL 2012 enterprise which has AlwaysOn and replication configured and running. It is a 4 node active-passive and the distributor on a separate physical server and subscribers also on separate servers as well. They all are SQL 2012 enterprise. I like to upgrade them to SQL 2014. Based on the 2014 SQL upgrade knowledge base (https://msdn.microsoft.com/en-us/library/ms143699.aspx?f=255&MSPPError=-2147217396). The disbributor has to be higher or equal to the publisher db server. With that in mind, I would upgrade the distributor SQL server first to SQL 2014. Then I would upgrade the publisher database server (the four nodes) next. This article also mentioned that I need to make sure nobody is making data changes on publisher dbs before I run the upgrade. Is this true and why?
The reason I am second guessing this requirement is that while I am upgrading the distributor, if the distribution db becomes unavailable for a short period of time, that would be ok and once the upgrade is done, all the data changes would be read by the log reader again. Isn't it what it supposed to do? I would think it is just like the situation when I am doing a reboot on the distributor database server.
Please explain why I need to stop users making data changes to the publisher dbs when I upgrade SQL 2012 replication to SQL 2014 as this would imply a scheduled downtime is required.
Thanks in advance,
OD
Ocean Deep