I don't know whether automatic failback is even a thing.  But even if it were, how would you want it to work - for failback to occur immediately the primary...

Why are you doing this row by row instead of as a set.

When you insert a NULL value, it doesn't have inverted commas round it in the INSERT...

Yes, or create the temp table before you start, instead of doing a SELECT INTO.  I always think that's safer.

John

Do you have an actual execution plan from a long-running delete that you could post here, please?

John

No backup and restore is necessary - Availability Groups are a high availability technology.  When your primary site is no longer available, your databases will automatically fail over to the...

You might also consider using the MAP toolkit.

John

If your database is read-only then your log file is not going to be used much and you're not going to need point-in-time recovery, so there's no harm in having...

Have a look at the index usage stats DMV.  Any index that is being written to often and read from rarely is a potential performance harmer.  Even then, it's going...

You could try something like this.

John

It depends.  Usually the second index would be sufficient for both queries.  However, if it's a requirement that both queries run in the absolute minimum time possible, you may want...

Just put the minus sign in the dynamic SQL, like this:
... DATEADD(HOUR, -'+CONVERT(CHAR(2),@timeoffset)+ ...

I've got to ask, though - why do you need dynamic SQL...

It won't affect indexing, no, but Eddie is right - it does affect memory grants, which in turn affects performance.  I overlooked that in my first reply.

LEN() returns...

Probably not, although it may affect data integrity.  If the maximum length of any value in the column is going to be 50, then you don't want varchar(300) for that...

No, do transaction logs hourly if, for example, you can only afford to lose an hour of data in the event of a disaster.

Checkpoints occur automatically every minute...

You don't even have consistent table names in there.  Sometimes you have 10032018 in the table name and sometimes you don't.  If you don't care about your code, nobody else...