Error: 21407, Severity: 16, Cannot create the subscription. If you specify a value of “initialize with backup” for the @sync_type parameter, you must subscribe to all articles in the publication by specifying a value of “all” for the @article parameter.
Error: 21408, Severity: 16, Cannot create the subscription. You must specify a value of “Active” or “Subscribed” for the @status parameter. This is because the value specified for the @sync_type parameter is “initialize with backup” or “replication support only”.

Error: 21409, Severity: 16, Only one of parameters %s and %s can be set.
Error: 21410, Severity: 16, Snapshot Agent startup message.
Error: 21411, Severity: 16, Distribution Agent startup message.
Error: 21412, Severity: 16, Merge Agent startup message.

Error: 21413, Severity: 16, Failed to acquire the application lock indicating the front of the queue.
Error: 21414, Severity: 10, Unexpected failure acquiring an application lock. Ensure that the account under which the Merge Agent runs is a member of the publication access list. If there is a lot of activity on the server, run the Merge Agent when there are more server resources av
Error: 21415, Severity: 10, Unexpected failure releasing an application lock. Ensure that the account under which the Merge Agent runs is a member of the publication access list. If there is a lot of activity on the server, run the Merge Agent when there are more server resources av
Error: 21416, Severity: 10, Property ‘%s’ of article ‘%s’ cannot be changed.
Error: 21417, Severity: 10, Having a queue timeout value of over 12 hours is not allowed.
Error: 21419, Severity: 10, Filter ‘%s’ of article ‘%s’ cannot be changed.
Error: 21420, Severity: 10, Subscription property ‘%s’ cannot be changed.
Error: 21421, Severity: 10, Article ‘%s’ cannot be dropped because there are other articles using it as a join article.
Error: 21422, Severity: 16, Queue Reader Agent startup message.
Error: 21423, Severity: 16, Either the publication ‘%s’ does not exist or you do not have sufficient permissions to access it. Ensure that the publication exists and that the account under which the Merge Agent connects to the Publisher is included in the publication access list (PA
Error: 21424, Severity: 16, The @publisher parameter must be NULL for SQL Server publishers.
Error: 21425, Severity: 16, The @publisher parameter may not be NULL for heterogeneous publishers.
Error: 21426, Severity: 16, No shared agent subscription exists for publication ‘%s’ and the subscriber/subscriber database pair ‘%s’/’%s’.
Error: 21450, Severity: 16, The replication %s could not be upgraded for %s databases. Ensure that %s is upgraded and execute %s again.

This is applicable on below versions of SQL Server

SQL Server 2005
SQL Server 2008 R2
SQL Server 2012
SQL Server 2014

Hope this was helpful.

Thanks,
SQLServerF1 Team
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