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title sys.dm_db_log_info (Transact-SQL) | Microsoft Docs
ms.custom
ms.date 04/24/2018
ms.prod sql
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ms.suite sql
ms.technology system-objects
ms.tgt_pltfrm
ms.topic conceptual
f1_keywords
sys.dm_db_log_info
sys.dm_db_log_info_TSQL
dm_db_log_info
dm_db_log_info_TSQL
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TSQL
helpviewer_keywords
sys.dm_db_log_info dynamic management view
ms.assetid f6b40060-c17d-472f-b0a3-3b350275d487
caps.latest.revision 4
author savjani
ms.author pariks
manager ajayj
monikerRange >= sql-server-2016 || = sqlallproducts-allversions

sys.dm_db_log_info (Transact-SQL)

[!INCLUDEtsql-appliesto-2016sp2-asdb-xxxx-xxx-md]

Returns virtual log file (VLF) information of the transaction log. Note all transaction log files are combined in the table output. Each row in the output represents a VLF in the transaction log and provides information relevant to that VLF in the log.

Syntax

sys.dm_db_log_info ( database_id )

Arguments

database_id | NULL | DEFAULT
Is the ID of the database. database_id is int. Valid inputs are the ID number of a database, NULL, or DEFAULT. The default is NULL. NULL and DEFAULT are equivalent values in the context of current database.

Specify NULL to return VLF information of the current database.

The built-in function DB_ID can be specified. When using DB_ID without specifying a database name, the compatibility level of the current database must be 90 or greater.

Table Returned

Column name Data type Description
database_id int Database ID.
file_id smallint File id of the transaction log.
vlf_begin_offset bigint Offset location of the virtual log file (VLF) from the beginning of the transaction log file.
vlf_size_mb float virtual log file (VLF) size in MB, rounded to 2 decimal places.
vlf_sequence_number bigint virtual log file (VLF) sequence number in the created order. Used to uniquely identify VLFs in log file.
vlf_active bit Indicates whether virtual log file (VLF) is in use or not.
0 - VLF is not in use.
1 - VLF is active.
vlf_status int Status of the virtual log file (VLF). Possible values include
0 - VLF is inactive
1 - VLF is initialized but unused
2 - VLF is active.
vlf_parity tinyint Parity of virtual log file (VLF).Used internally to determine the end of log within a VLF.
vlf_first_lsn nvarchar(48) Log sequence number (LSN) of the first log record in the virtual log file (VLF).
vlf_create_lsn nvarchar(48) Log sequence number (LSN) of the log record that created the virtual log file (VLF).

Remarks

The sys.dm_db_log_info dynamic management function replaces the DBCC LOGINFO statement.

Permissions

Requires the VIEW DATABASE STATE permission in the database.

Examples

A. Determing databases in a SQL Server instance with high number of VLFs

The following query determines the databases with more than 100 VLFs in the log files, which can affect the database startup, restore, and recovery time.

SELECT [name], COUNT(l.database_id) AS 'vlf_count' 
FROM sys.databases s
CROSS APPLY sys.dm_db_log_info(s.database_id) l
GROUP BY [name]
HAVING COUNT(l.database_id) > 100

B. Determing the position of the last VLF in transaction log before shrinking the log file

The following query can be used to determine the position of the last active VLF before running shrinkfile on transaction log to determine if transaction log can shrink.

USE AdventureWorks2016
GO

;WITH cte_vlf AS (
SELECT ROW_NUMBER() OVER(ORDER BY vlf_begin_offset) AS vlfid, DB_NAME(database_id) AS [Database Name], vlf_sequence_number, vlf_active, vlf_begin_offset, vlf_size_mb
	FROM sys.dm_db_log_info(DEFAULT)),
cte_vlf_cnt AS (SELECT [Database Name], COUNT(vlf_sequence_number) AS vlf_count,
	(SELECT COUNT(vlf_sequence_number) FROM cte_vlf WHERE vlf_active = 0) AS vlf_count_inactive,
	(SELECT COUNT(vlf_sequence_number) FROM cte_vlf WHERE vlf_active = 1) AS vlf_count_active,
	(SELECT MIN(vlfid) FROM cte_vlf WHERE vlf_active = 1) AS ordinal_min_vlf_active,
	(SELECT MIN(vlf_sequence_number) FROM cte_vlf WHERE vlf_active = 1) AS min_vlf_active,
	(SELECT MAX(vlfid) FROM cte_vlf WHERE vlf_active = 1) AS ordinal_max_vlf_active,
	(SELECT MAX(vlf_sequence_number) FROM cte_vlf WHERE vlf_active = 1) AS max_vlf_active
	FROM cte_vlf
	GROUP BY [Database Name])
SELECT [Database Name], vlf_count, min_vlf_active, ordinal_min_vlf_active, max_vlf_active, ordinal_max_vlf_active,
((ordinal_min_vlf_active-1)*100.00/vlf_count) AS free_log_pct_before_active_log,
((ordinal_max_vlf_active-(ordinal_min_vlf_active-1))*100.00/vlf_count) AS active_log_pct,
((vlf_count-ordinal_max_vlf_active)*100.00/vlf_count) AS free_log_pct_after_active_log
FROM cte_vlf_cnt
GO

See Also

Dynamic Management Views and Functions (Transact-SQL)
Database Related Dynamic Management Views (Transact-SQL)
sys.dm_db_log_space_usage (Transact-SQL)
sys.dm_db_log_stats (Transact-SQL)