how to avoid incidents on Drive getting full due to transaction log getting full

1. Check recovery model

• Full Recovery model keeps all log entries until a log backup occurs.
• If you don't take regular log backups, the log will just keep growing. If you don't need point-in-time recovery, consider switching to Simple Recovery Model.

ALTER DATABASE [YourDB] SET RECOVERY SIMPLE;

2. Schedule regular log backups

• If you need Full Recovery, you must run transaction log backups frequently.
• This truncates inactive portions of the log and prevents growth. Example SQL Agent job:

BACKUP LOG [YourDB] TO DISK = 'E:\SQLBackups\YourDB_Log.trn' WITH INIT;

Schedule every 15 minutes (or based on workload).

3. Monitor log reuse waits

Check why the log isn't being reused:

DBCC SQLPERF(LOGSPACE);
SELECT name, log_reuse_wait_desc 
FROM sys.databases;

Common blockers:

• LOG_BACKUP → No log backup taken
• ACTIVE_TRANSACTION → A long-running transaction is preventing truncation
• REPLICATION → Replication not keeping up
• AVAILABILITY_REPLICA → AG/replica sync issues

4. Manage long-running transactions

• Open transactions (ETL, batch jobs, index rebuilds) keep log records until they finish.
• Identify them with:

DBCC OPENTRAN([YourDB]);

5. Size and autogrowth settings

• Pre-size log file to expected needs rather than letting it grow in small increments.
• Avoid percentage autogrowth; use fixed MB growth (e.g., 512MB).

6. Regular maintenance

• Ensure index maintenance and large updates are batched to avoid massive log usage.
• If rebuilding indexes, consider ONLINE = ON and SORT_IN_TEMPDB = ON to reduce log impact.

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hth

Marcin