SQL Server 2008 R2 Restore COPY_ONLY full backup with transaction logs

A full backup in SQL Server 2008 does not break the log chain. It only resets the differential base-lsn.

You also can restore log backups after restoring from a copy only. The following script demos that:

CREATE DATABASE BakTst13;
GO
ALTER DATABASE BakTst13 SET RECOVERY FULL;
GO
USE BakTst13;
GO
CREATE TABLE dbo.tst(id INT IDENTITY(1,1));
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Full_1' WITH INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP LOG BakTst13 
TO DISK = 'BakTst13_Log_1' WITH INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Full_2' WITH INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Full_C' WITH COPY_ONLY,INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP LOG BakTst13 
TO DISK = 'BakTst13_Log_2' WITH INIT,FORMAT;
GO
USE tempdb;
GO
DROP DATABASE BakTst13;
GO
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Full_1' WITH NORECOVERY;
RESTORE LOG BakTst13 FROM DISK='BakTst13_Log_1' WITH NORECOVERY;
RESTORE LOG BakTst13 FROM DISK='BakTst13_Log_2' WITH RECOVERY;
GO
SELECT * FROM BakTst13.dbo.tst;
GO
DROP DATABASE BakTst13;
GO
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Full_C' WITH NORECOVERY;
RESTORE LOG BakTst13 FROM DISK='BakTst13_Log_2' WITH RECOVERY;
GO
SELECT * FROM BakTst13.dbo.tst;
GO
DROP DATABASE BakTst13;

It creates a database and a table and inserts 50 rows into that table. In between those inserts several backups are taken in this order:

  1. Full
  2. Log
  3. Full
  4. Full Copy_Only
  5. Log

Next the database is dropped and restored like this:

  1. 1st Full
  2. 1st Log
  3. 2nd Log

The following SELECT demonstrates that the restore was successful.

This shows that neither a COP_ONLY nor a normal Full Backup break the log chain.

Then the database is dropped again and restored like this:

  1. Copy_Only Full
  2. 2nd Log

Afterwards the SELECT demonstrates success again.

This demonstrates that you can use a COPY_ONLY full backup as the base of your Log Restore.

Differential tests

I created a DIFFERENTIAL version too:

CREATE DATABASE BakTst13;
GO
ALTER DATABASE BakTst13 SET RECOVERY FULL;
GO
USE BakTst13;
GO
CREATE TABLE dbo.tst(id INT IDENTITY(1,1));
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Full_1' WITH INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Diff_1' WITH DIFFERENTIAL,INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Full_2' WITH INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Diff_2' WITH DIFFERENTIAL,INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Full_C' WITH COPY_ONLY,INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Diff_3' WITH DIFFERENTIAL,INIT,FORMAT;
GO
USE tempdb;
GO
DROP DATABASE BakTst13;
GO
RAISERROR('------> Starting restore F1, D1, D2',0,1)WITH NOWAIT;
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Full_1' WITH NORECOVERY; 
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Diff_1' WITH NORECOVERY;
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Diff_2' WITH NORECOVERY;--<--Fails!
GO
DROP DATABASE BakTst13;
GO
RAISERROR('------> Starting restore FC, D3',0,1)WITH NOWAIT;
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Full_C' WITH NORECOVERY;
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Diff_3' WITH NORECOVERY;--<--Fails!
GO
DROP DATABASE BakTst13;
GO
RAISERROR('------> Starting restore F2, D2, D3',0,1)WITH NOWAIT;
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Full_2' WITH NORECOVERY; 
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Diff_2' WITH NORECOVERY;
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Diff_3' WITH RECOVERY;
GO
SELECT * FROM BakTst13.dbo.tst;
GO
DROP DATABASE BakTst13;

This takes backups in this order:

  1. 1st Full
  2. 1st Differential
  3. 2nd Full
  4. 2nd Differential
  5. Copy_Only Diff
  6. 3rd Differential

It then tries this restore route:

  1. 1st Full
  2. 1st Differential
  3. 2nd Differential

Step 3 fails with this error:

Msg 3136, Level 16, State 1, Line 4
This differential backup cannot be restored because the database has not been restored to the correct earlier state.

This shows that a normal full backup breaks the differential chain.

Next the database is dropped and this restore flow is attempted:

  1. Copy_Only Full
  2. 3rd Differential

Step 2 fails with the same error as step 3 above. This shows that a copy only backup cannot be used as the base for a differential restore.

Then the database is dropped again and the following restore is executed:

  1. 2nd Full
  2. 2nd Differential
  3. 3rd Differential

The following select proves that this restore succeeded. This shows that a COPY_ONLY Full backup does not interrupt the differential chain.


Here's what happens when differentials are involved:

CREATE DATABASE BakTst13;
GO
ALTER DATABASE BakTst13 SET RECOVERY FULL;
GO
USE BakTst13;
GO
CREATE TABLE dbo.tst(id INT IDENTITY(1,1));
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10 -- 10 rows so far
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Full_1' WITH INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10 -- 20 rows so far
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Diff_1' WITH INIT,FORMAT,DIFFERENTIAL
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10 -- 30 rows so far
BACKUP LOG BakTst13 
TO DISK = 'BakTst13_Log_1' WITH INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10 -- 40 rows so far
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Full_2' WITH INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10 -- 50 rows so far
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Full_C' WITH COPY_ONLY,INIT,FORMAT;
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10 -- 60 rows so far
GO
BACKUP DATABASE BakTst13 
TO DISK = 'BakTst13_Diff_2' WITH INIT,FORMAT,DIFFERENTIAL
GO
INSERT INTO dbo.tst DEFAULT VALUES
GO 10 -- 70 rows so far
GO
BACKUP LOG BakTst13 
TO DISK = 'BakTst13_Log_2' WITH INIT,FORMAT;
GO


USE tempdb;
GO
DROP DATABASE BakTst13;
GO
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Full_2' WITH NORECOVERY;
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Diff_2' WITH NORECOVERY;
RESTORE LOG BakTst13 FROM DISK='BakTst13_Log_2' WITH RECOVERY;
GO
SELECT COUNT(*) FROM BakTst13.dbo.tst; -- Must be 70: log chain not broken
GO
DROP DATABASE BakTst13;
GO
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Full_C' WITH NORECOVERY;
RESTORE LOG BakTst13 FROM DISK='BakTst13_Log_2' WITH RECOVERY;
GO
SELECT COUNT(*) FROM BakTst13.dbo.tst; -- Must be 70
GO
DROP DATABASE BakTst13;

In a word: yes, you can use a COPY_ONLY backup to restore further log backups. What you cannot do is use the COPY_ONLY backup as a differential base. That means you will not be able to restore any differential backups on the restored COPY_ONLY backup:

DROP DATABASE BakTst13;
GO
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Full_C' WITH NORECOVERY;
RESTORE DATABASE BakTst13 FROM DISK='BakTst13_Diff_2' WITH NORECOVERY;

If you try this, you will get an error:

Processed 160 pages for database 'BakTst13', file 'BakTst13' on file 1.
Processed 2 pages for database 'BakTst13', file 'BakTst13_log' on file 1.
RESTORE DATABASE successfully processed 162 pages in 0.009 seconds (139.811 MB/sec).
Msg 3136, Level 16, State 1, Line 2
This differential backup cannot be restored because the database has not been restored to the correct earlier state.
Msg 3013, Level 16, State 1, Line 2
RESTORE DATABASE is terminating abnormally.

Differential backups can be hard to understand and can fool even experienced DBAs.

Tags:

Backup

Transaction Log

Sql Server 2008

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