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Assessing SQL Server 2017 Cumulative Update 22: A Frustrating Lack of Documentation


Microsoft has released Cumulative Update 22 for SQL Server 2017, which includes various fixes. However, many of the bug fixes don’t have detailed KB articles, making it difficult to determine if they are relevant to specific workloads. For instance, one fix enables QDS instance level memory limits by default on box edition, which prevents QDS from consuming more memory after a certain limit by changing to READ ONLY mode. Unfortunately, Microsoft hasn’t explained why the Query Store goes into read-only mode, what box edition is, or what the limits are, which is frustrating for users of enterprise database software that costs $7,000 per core.

The lack of quality documentation is unacceptable for such expensive software, and it can be difficult to trust updates that turn off features like the Query Store without any explanation. There are other fixes in CU22, including managed backup not backing up the database when SQL Agent system jobs are changed to a name other than ‘sa,’ being unable to restore SQL Server database from previous versions on NVMe device partitioned in 4K block size, and incorrect results occurring when running linked server query with aggregates or joins on table with a filtered index on a remote server in SQL Server 2017.

Other issues addressed in CU22 include COMPILE blocking, Full-Text search auto crawl stops when AG goes offline, and concurrent inserts against tables with columnstore indexes causing queries to hang in SQL Server. Fixes have also been made for upgrade script fails if you use Always On Failover Cluster Instance as a secondary replica in SQL Server, and SQL Server fails to start when remote admin connections are enabled, and IPV6 is disabled on the host. Additionally, an access violation exception occurs in Availability Groups in SQL Server 2017 under specific conditions.

In conclusion, Cumulative Update 22 for SQL Server 2017 has some notable fixes, but the lack of documentation makes it difficult to determine if they are relevant to specific workloads. Hopefully, Microsoft will start documenting these changes more thoroughly in the future to provide better transparency and increase trust in their updates. If you are considering installing CU22, be aware of the lack of documentation and proceed with caution. The update can be downloaded from the Microsoft Support site.