Need to update primary from 2019-CU14 to 2019 CU15 and a few hours/days later update secondary to CU 15 once the primary is deemed stable. Can you safely log ship between primary and secondary servers on different cumulative update versions (CU-15 to CU-14 in this case)?
Below are the methods you can try. The first solution is probably the best. Try others if the first one doesn’t work. Senior developers aren’t just copying/pasting – they read the methods carefully & apply them wisely to each case.
You can see Microsoft recommendations on the Upgrading Log Shipping to SQL Server 2016 doc:
To preserve your log shipping disaster recovery solution, upgrade, or
apply servicing updates in the appropriate order. Servicing updates
include service packs or cumulative updates.
The doc gives some specific info related to the upgrade and the order is the opposite of the one you intend to apply the update on your environment:
The upgrade process involves upgrading the secondary server instances
of SQL Server before upgrading the primary server instance. Always
upgrade the secondary SQL Server instances first. Log shipping
continues throughout the upgrade process because the upgraded
secondary server instances continue to restore the log backups from
primary server instance. If the primary server instance is upgraded
before the secondary server instance, log shipping will fail because a
backup created on a newer version of SQL Server cannot be restored on
an older version of SQL Server. You can upgrade the secondary
instances simultaneously or serially, but all secondary instance must
be upgraded before the primary instance is upgraded to avoid a log
Yes you can. I have done it in every version of sql server since 2005 including 2019. You can have primary and secondary at any CU level, although it is recommended your secondary is upgraded prior to the primary.