Managing SQL Server ERRORLOG File Growth to Prevent Space Issues

 Problem Overview:

In one of our smaller production environments, the SQL Server ERRORLOG file size unexpectedly grew to almost 60 GB. This caused a critical space crunch on the C:\ drive, leading to application timeout errors. The ERRORLOG file was located at:

C:\Program Files\Microsoft SQL Server\MSSQL14.INST1\MSSQL\Log

Challenges:

Active ERRORLOG File: The current ERRORLOG file could not be deleted directly because it was actively being used by SQL Server.

Time Constraints: Restarting the SQL Server instance to create a new ERRORLOG file required approval from the client and the change management team, which could be time-consuming.

Resolution Steps:

Step 1: Cycle the ERRORLOG File Without Restarting SQL Server

To address the issue without a service restart, we used the following command:

EXEC sp_cycle_errorlog;

GO

This command immediately created a new ERRORLOG file. The active log was cycled, and the previous ERRORLOG file was moved to the same directory with a numbered suffix (e.g., ERRORLOG.1).

Step 2: Relocate and Manage Old ERRORLOG Files

The old ERRORLOG file, which was consuming significant space, was manually moved to a different drive with sufficient free space. This provided temporary relief for the space issue on the C:\ drive. After a few days, we deleted the old log files to reclaim space permanently.

Step 3: Identify and Fix the Root Cause

Upon investigation, we discovered that one of the SQL Server Agent jobs was generating excessive logs in the ERRORLOG file. The problematic statement in the job's code was identified and removed to prevent further excessive logging.

Key Takeaways:

Proactive Monitoring: Regular monitoring of SQL Server ERRORLOG file size and disk space utilization is crucial to avoid unexpected space issues.

Efficient Log Management: Use the sp_cycle_errorlog procedure periodically to cycle logs and prevent single ERRORLOG files from growing too large.

Root Cause Analysis: Always investigate the underlying cause of excessive logging to implement a permanent fix.