Cycle SQL Server Errorlog

The standard SQL Server Errorlog has six generations and is recycled implicit by a service restart.
This might be an issue when the database instance Login auditing is „Both failed and successful logins“ (Full), because the Errorlog will contain 100000+ entries.
I have several times seen more than a million entries.
A Errorlog of this size it takes some time to open in SQL Server Management Studio.
You could „cheat“ by opening it in a editor on a UNC path. This could require an editor that can handle a file larger than 1 GB.

With only six generations of the Errorlog, you will experience to loose the last usefull Errlog when the instance is restarted a handfull times. This will happen when a patch is failing, power blackout or another unpleasent event.
Configure SQL Server Error Logs.
To make the Errorlog available I have increased the number of generations.
This can be done using SQL Server Management Studio by expanding the database instance in the Object Explorer and expanding the „Management“ section. Right-click on „SQL Server Logs“ and click „Configure“.
Then enter the number of Errorlog generations (see figure „Configure SQL Server Error Logs“).

The number of Errorlog generations can not be altered by sp_configure or an ALTER statement, but in the Registry.

To make the Errorlog available I have also sheduled a recycle every day at 23:59:30. Recycling at this time gives the Errorlog a timestamp matching the day it contains log entries from.

The two tasks above can be done using this T-SQL script:
EXECUTE [master].[sys].[xp_instance_regwrite]
@key = N'Software\Microsoft\MSSQLServer\MSSQLServer',
@value_name = N'NumErrorLogs',
@type = N'REG_DWORD',
@value = N'42';

DECLARE @sa_name sysname = ( -- Name of 'sa' account in hardended installation
SELECT [server_principals].[name]
FROM [master].[sys].[server_principals]
WHERE [server_principals].[principal_id] = 1
EXECUTE [msdb].[dbo].[sp_add_job]
@job_name = N'MsSqlDbErrorlogCycle',
@enabled = 1,
@notify_level_eventlog = 2,
@notify_level_email = 2,
@notify_level_netsend = 2,
@notify_level_page = 2,
@delete_level = 0,
@description = N'Cycle SQL Server Database Engine Errorlog.
Created by Niels Grove-Rasmussen.',
@category_name = N'Database Maintenance',
@owner_login_name = @sa_name,
@job_id = @jobId OUTPUT;
EXECUTE [msdb].[dbo].[sp_add_jobserver]
@job_name = N'MsSqlDbErrorlogCycle';
EXECUTE [msdb].[dbo].[sp_add_jobstep]
@job_name = N'MsSqlDbErrorlogCycle',
@step_name = N'Execute MsSqlDbErrorlogCycle',
@step_id = 1,
@cmdexec_success_code = 0,
@on_success_action = 1,
@on_fail_action = 2,
@retry_attempts = 0,
@retry_interval = 0,
@os_run_priority = 0,
@subsystem = N'TSQL',
@command = N'EXECUTE [master].[dbo].[sp_cycle_errorlog];',
@database_name = N'master',
@flags = 4;
EXECUTE [msdb].[dbo].[sp_update_job]
@job_name = N'MsSqlDbErrorlogCycle',
@notify_level_eventlog = 2,
@notify_level_email = 2,
@notify_level_netsend = 2,
@notify_level_page = 2,
@delete_level = 0,
@description = N'Cycle SQL Server Database Engine Errorlog',
@category_name = N'Database Maintenance',
@owner_login_name = @sa_name;
DECLARE @schedule_id INT;
EXECUTE [msdb].[dbo].[sp_add_jobschedule]
@job_name = N'MsSqlDbErrorlogCycle',
@name = N'Schedule MsSqlDbErrorlogCycle',
@freq_type = 4,
@freq_interval = 1,
@freq_subday_type = 1,
@freq_subday_interval = 0,
@freq_relative_interval = 0,
@freq_recurrence_factor = 1,
@active_start_time = 235930,
@schedule_id = @schedule_id OUTPUT;


2010-06-08  First blog entry.
2013-11-19  Name of sa–principal in local variable.

No comments: