SQL Server -Tail Log Backups

Tail Log Backup: Tail Log Back up is Back up of Tail of Log Just Before Before Restore operation of Database.

  • As it is Log Backup so we can take Tail Log Backup when recovery model Database either Full or Bulk Logged.

Like any log backup, a tail-log backup is taken by using the BACKUP LOG statement and it is  recommend that you take a tail-log backup in the following situations:

  • If the database is online and you plan to perform a restore operation on the database, before starting the restore operation, back up the tail of the log using WITH NORECOVERY:
    
    BACKUP LOG database_name TO <backup_device> WITH NORECOVERY
    
    -- If the database is damaged, use WITH CONTINUE_AFTER_ERROR, as follows:
    
    BACKUP LOG database_name TO <backup_device> WITH CONTINUE_AFTER_ERROR
    
    
  • Tail Lob Backup capture the tail of log even database is in offline mode,Database is damaged or missing data file.This might cause incomplete metadata from the restore information commands and msdb. However, only the metadata is incomplete; the captured log is complete and usable.
  • If a tail-log backup has incomplete metadata, in the backupset table, has_incomplete_metadata is set to 1. Also, in the output of RESTORE HEADERONLY, HasIncompleteMetadata is set to 1.
  • If the metadata in a tail-log backup is incomplete, the backupfilegroup table will be missing most of the information about filegroups at the time of the tail-log backup. Most of the backupfilegroup table columns are NULL.

 

 

 

 

 

 

SQL Server-BackUp History

Many times we need backup history, when which type of backup is taken?

Is back up was compressed? So I think let me make a Script which gives list of backup history.

Let me share One interesting fact which I observed when I was working on  this Script.

Let me describe scenario.


  • We have two server 1.Test server and 2.Local server
  • I need to restore database on Local serer from Test server.
  • But Database does not exist on Local server.
  • So I will create new database.Then Restore Full back up which is taken from Test server.
  • now i will run following script for newly created and restored database.
  • Note it will show one record for which database is restored.
  • Reason is very simple cause it is backup right now for newly created Database as well as it is for Test server.as we have restored database to Local server from backup.so it will show one record for backup history on Local server without taking backup.
SELECT  ms.software_name [software] ,
		s.user_name ,
        s.database_name ,
        CASE ms.is_compressed
          WHEN 1 THEN 'Compressed'
          ELSE 'DeCompressed'
        END AS [BackupMethod] ,
         s.recovery_model ,
        CASE s.type
          WHEN 'D' THEN 'FULL'
          WHEN 'L' THEN 'Transaction Log'
          WHEN 'I' THEN 'Differential'
        END AS BackupType ,
        m.physical_device_name ,
        CASE ms.is_compressed
          WHEN 1
          THEN CAST(s.compressed_backup_size / 1048576 AS NUMERIC(18, 2))
          ELSE CAST(s.backup_size / 1048576 AS NUMERIC(18, 2))
        END AS [Size in MB] ,

        s.backup_start_date ,
        CAST(DATEDIFF(s, s.backup_start_date, s.backup_finish_date) AS VARCHAR(4)) TimeTaken ,
        s.first_lsn ,
        s.last_lsn ,
        s.server_name
FROM    msdb.dbo.backupset s
        INNER JOIN msdb.dbo.backupmediafamily m ON s.media_set_id = m.media_set_id
        INNER JOIN msdb.dbo.backupmediaset ms ON ms.media_set_id = s.media_set_id
WHERE   s.database_name = DB_NAME()