SQL Server 2019 CU 2 breaks SQL Server Agent

[German]Nasty  surprise for administrators of Microsoft SQL Server 2019 who install the cumulative update 2 of February 13, 2020. This can kill the SQL Server Agent.

Cumulative Update 2 for SQL Server 2019

Cumulative Update 2 for SQL Server 2019 is available for both Linux and SQL Server 2019 on Windows. It was probably released on February 13, 2020 and contains fixes that were released after the initial release of SQL Server 2019. In addition, the SQL Server and Analysis Services components will be upgraded to the following builds:

• SQL Server: Version 15.0.4013.40, File Version: 2019.150.4013.40
• Analysis Services: Version 15.0.34.1, File Version: 2018.150.34.1

Microsoft recommends continuous, proactive installation of CUs as they become available according to the guidelines in the KB article.

CU2 breaks SQL Server Agent

The SQL Server Agent is responsible for executing jobs such as backups and other maintenance tasks and can be used with T-SQL for various purposes. Shortly after the CU2 was released, users reported this issue within the StackExchange DBA forum.

SQL Server Agent fails after installing SQL Server 2019 CU2

After installing CU2 our SQL server agent randomly stops working. If you go to check on the status of the agent by opening Job Activity Monitor, it comes up blank for a while then throws an error:

Failed to retrieve data for this request. (Microsoft.SqlServer.Management.Sdk.Sfc)

For help, click: https://go.microsoft.com/fwlink?ProdName=Microsoft%20SQL%20Server&LinkId=20476

—————————— ADDITIONAL INFORMATION:

An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)

---

A severe error occurred on the current command. The results, if any, should be discarded. (Microsoft SQL Server, Error: 0)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft%20SQL%20Server&ProdVer=15.00.4013
&EvtSrc=MSSQLServer&EvtID=0&LinkId=20476

Any clue what could be causing this?

Other users then pointed to this Azure feedback entry, and Microsoft then confirmed, they investigated it. A short time later the following information was given:

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.

The bug in CU2 will be fixed in CU3. Microsoft recommends that those affected go back to CU1. In the meantime, the KB article contains the confirmation of the bug, which was added on March 4, 2020:

Known issue

There is a known issue with SQL Server Agent in SQL Server 2019 CU2. This will be fixed in the next CU release (SQL Server 2019 CU3).

• If you are using SQL Server 2019 SQL Server Agent, it is advised to skip this CU upgrade, and wait for SQL Server 2019 CU3.
• If you have already applied SQL Server 2019 CU2 and are experiencing issues with SQL Server Agent, please revert to SQL Server 2019 CU1.

For further information, please refer to the KB article. Any of you affected by this issue?   (via)