During SQL Server patching is when the SQL Server service fails to start after applying a patch

 One of the most frequent issues DBAs face during SQL Server patching is when the SQL Server service fails to start after applying a patch. 

This can be caused by various factors, such as corrupted system databases, incompatible configuration changes, or issues with disk space or permissions.

𝗧𝗵𝗲 𝗜𝘀𝘀𝘂𝗲:

After applying Cumulative Updates or Service Packs, many DBAs experience failures where the SQL Server service doesn’t restart or the instance won’t come online. 

The root cause could range from corrupted system databases (like master, msdb, or model) to configuration conflicts or permission issues.

𝗖𝗼𝗺𝗺𝗼𝗻 𝗖𝗮𝘂𝘀𝗲𝘀:

Corrupted system databases (master, msdb)

Incompatible configuration or parameter changes

Missing or incorrect permissions for SQL Server service account

Disk space issues or problems with SQL Server file access

Registry or dependency issues affecting the service

𝗥𝗲𝘀𝗼𝗹𝘂𝘁𝗶𝗼𝗻 𝗦𝘁𝗲𝗽𝘀:

𝗖𝗵𝗲𝗰𝗸 𝗘𝗿𝗿𝗼𝗿 𝗟𝗼𝗴𝘀: Review SQL Server Error Logs and Windows Event Logs for specific errors.

𝗥𝗲𝘀𝘁𝗼𝗿𝗲 𝗦𝘆𝘀𝘁𝗲𝗺 𝗗𝗮𝘁𝗮𝗯𝗮𝘀𝗲𝘀: If corruption is detected, restore from a known good backup of system databases.

𝗖𝗵𝗲𝗰𝗸 𝗖𝗼𝗻𝗳𝗶𝗴𝘂𝗿𝗮𝘁𝗶𝗼𝗻: Ensure no conflicts with new settings introduced by the patch. Verify memory settings, tempdb, and other configurations.

𝗩𝗲𝗿𝗶𝗳𝘆 𝗣𝗲𝗿𝗺𝗶𝘀𝘀𝗶𝗼𝗻𝘀: Ensure the SQL Server service account has the necessary access to files and directories.

𝗗𝗶𝘀𝗸 𝗦𝗽𝗮𝗰𝗲: Confirm sufficient disk space, especially for tempdb and transaction logs.

𝗥𝗲𝗮𝗽𝗽𝗹𝘆 𝗣𝗮𝘁𝗰𝗵 𝗼𝗿 𝗥𝗲𝗽𝗮𝗶𝗿 𝗜𝗻𝘀𝘁𝗮𝗹𝗹𝗮𝘁𝗶𝗼𝗻: If needed, reapply the patch or use SQL Server Setup to perform a repair.

𝗥𝗼𝗹𝗹𝗯𝗮𝗰𝗸 𝗣𝗮𝘁𝗰𝗵 (𝗶𝗳 𝗻𝗲𝗲𝗱𝗲𝗱): If the issue persists, rollback the patch or restore from backup.

𝗣𝗿𝗲𝘃𝗲𝗻𝘁𝗶𝗼𝗻 𝗧𝗶𝗽𝘀:

Always test patches in a non-prod environment first.

Backup critical system databases, especially master, before applying patches.

Document configurations before patching and monitor disk space and logs to detect issues early.

Patching is critical for SQL Server security and performance, but it’s vital to ensure a smooth patching process with proactive steps. Let’s keep SQL environments healthy and running!