Microsoft has admitted that Cumulative Update 2 for SQL Server 2019 has a problem, and those using SQL Server Agent should either skip it or roll it back.
Cumulative Update 2 appeared on 13 February and contains all manner of important fixes for database botherers aimed at boosting performance and improving stability.
Alas, things seemed to go wrong pretty quickly for some database admins as users took to the DBA forums in StackExchange to complain that the SQL Server Agent seemed a bit poorly after applying the update.
Seemingly random failures, problems with schedules and freezes were mentioned as users struggled to get to grips with what was going wrong. Microsoft's own forums were similarly blighted, with one user making the important point: "In addition to not showing jobs they are also not being run so important jobs such as backups aren't being done."
SQL Server Agent is responsible for running jobs such as backups and other maintenance tasks. It can also be found running T-SQL for all manner of purposes, so for it to be broken is not ideal.
After a period of protracted silence, Microsoft admitted: "The bug introduced in CU2 with
xp_sqlagent_enum_jobs is now understood and a fix will ship in CU3. Meanwhile, if you're hitting this issue, revert back to CU1. We apologize for any inconvenience we may have caused."
SQL guru Brent Ozar observed in a blog post: "We were all pretty surprised that Agent would break when it wasn't even supposedly changed in this CU", along with a picture of himself holding the retail packaging for SQL Server 6.5.
Ah, those were the days.
For now, the advice for affected SQL Server 2019 Agent users is to stick with Cumulative Update 1 for the time being. CU3 is likely to hit during March and deal with the problem (and hopefully not break anything else.)
CU2, however, did include some useful fixes. As one of Ozar's commenters observed regarding installing the thing: "Damned if I do and damned if I don't." ®