It took me more than half hour to figure out how to start an XEvents trace on a read-scale out instance of Azure SQL Managed Instance. It’s hard to monitor read scale-out instances, so tracing is desirable! I started with a simple trace of sql_statement_completed. Hopefully this saves other folks some time.
If you use readable secondaries in Availability Groups or Read-Scale out instances in Azure SQL Managed Instance, you may have queries fail repeatedly if there is a glitch and statistics are not successfully ‘refreshed’ on the secondary replica. Those queries may keep failing until you manually intervene.
It’s unclear if Microsoft will ever fix this. There is a well established support deflection article which documents the issue and provides ‘workarounds’.
The Business Critical service tier in Azure SQL Managed Instance is a lot more expensive than General Purpose. For the extra money, you get a different architecture.
Is it worth the extra cost? Spoiler: your mileage will vary, but probably not. Let’s talk about why.
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