sys.dm_db_log_stats (Transact-SQL)
Applies to:
SQL Server 2016 (13.x) SP 2 and later
Azure SQL Database
Azure SQL Managed Instance
Returns summary level attributes and information on transaction log files of databases. Use this information for monitoring and diagnostics of transaction log health.
Transact-SQL syntax conventions
Syntax
sys.dm_db_log_stats ( 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.
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.
Tables Returned
Column name | Data type | Description |
---|---|---|
database_id | int | Database ID. In Azure SQL Database, the values are unique within a single database or an elastic pool, but not within a logical server. |
recovery_model | nvarchar(60) | Recovery model of the database. Possible values include: SIMPLE BULK_LOGGED FULL |
log_min_lsn | nvarchar(24) | Current start log sequence number (LSN) in the transaction log. |
log_end_lsn | nvarchar(24) | log sequence number (LSN) of the last log record in the transaction log. |
current_vlf_sequence_number | bigint | Current virtual log file (VLF) sequence number at the time of execution. |
current_vlf_size_mb | float | Current virtual log file (VLF) size in MB. |
total_vlf_count | bigint | Total number of virtual log files (VLFs) in the transaction log. |
total_log_size_mb | float | Total transaction log size in MB. |
active_vlf_count | bigint | Total number of active virtual log files (VLFs) in the transaction log. |
active_log_size_mb | float | Total active transaction log size in MB. |
log_truncation_holdup_reason | nvarchar(60) | Log truncation holdup reason. The value is same as log_reuse_wait_desc column of sys.databases . (For more detailed explanations of these values, see The Transaction Log). Possible values include: NOTHING CHECKPOINT LOG_BACKUP ACTIVE_BACKUP_OR_RESTORE ACTIVE_TRANSACTION DATABASE_MIRRORING REPLICATION DATABASE_SNAPSHOT_CREATION LOG_SCAN AVAILABILITY_REPLICA OLDEST_PAGE XTP_CHECKPOINT OTHER TRANSIENT |
log_backup_time | datetime | Last transaction log backup time. |
log_backup_lsn | nvarchar(24) | Last transaction log backup log sequence number (LSN). |
log_since_last_log_backup_mb | float | Log size in MB since last transaction log backup log sequence number (LSN). |
log_checkpoint_lsn | nvarchar(24) | Last checkpoint log sequence number (LSN). |
log_since_last_checkpoint_mb | float | Log size in MB since last checkpoint log sequence number (LSN). |
log_recovery_lsn | nvarchar(24) | Recovery log sequence number (LSN) of the database. If log_recovery_lsn occurs before the checkpoint LSN, log_recovery_lsn is the oldest active transaction LSN, otherwise log_recovery_lsn is the checkpoint LSN. |
log_recovery_size_mb | float | Log size in MB since log recovery log sequence number (LSN). |
recovery_vlf_count | bigint | Total number of virtual log files (VLFs) to be recovered, if there was failover or server restart. |
Remarks
When running sys.dm_db_log_stats
against a database that is participating in an Availability Group as a secondary replica, only a subset of the fields described above will be returned. Currently, only database_id
, recovery_model
, and log_backup_time
will be returned when run against a secondary database.
Permissions
Requires the VIEW SERVER STATE
permission in the database.
Permissions for SQL Server 2022 and later
Requires VIEW SERVER PERFORMANCE STATE permission on the server.
Examples
A. Determining databases in a SQL Server instance with high number of VLFs
The following query returns the databases with more than 100 VLFs in the log files. Large numbers of VLFs can affect the database startup, restore, and recovery time.
SELECT name AS 'Database Name', total_vlf_count AS 'VLF count'
FROM sys.databases AS s
CROSS APPLY sys.dm_db_log_stats(s.database_id)
WHERE total_vlf_count > 100;
B. Determining databases in a SQL Server instance with transaction log backups older than 4 hours
The following query determines the last log backup times for the databases in the instance.
SELECT name AS 'Database Name', log_backup_time AS 'last log backup time'
FROM sys.databases AS s
CROSS APPLY sys.dm_db_log_stats(s.database_id);
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_info (Transact-SQL)
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