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After doing some research I cannot seem to find an answer to this question.

Background I am attempting to setup a backup plan that fits the following three requirements:

  1. Reliability of backups, having nightly full backups
  2. Transaction log backups that could be restored from
  3. Low amount of disc space used
  4. The backups must be accessible locally for an auditing tool

So to fit those needs I am thinking full backups weekly, differential daily, and transaction hourly. Then each night a copy_only backup would run that can be shipped offsite, this backup is done so that the log chain is not broken, and we have reliable nightly full backups offsite, without having to eat up so much local disc space.

Question Is it possible to restore from the copy_only backup, and restore the transaction logs after.

Let me just give an example so you know what I am talking about.

Using the below list I am wondering if it is possible to restore FullbackupCOPY_ONLYC.bak followed by TransactionbackupG.trn, TransactionbackupH.trn, finally TransactionbackupI.trn

> ---List of Backups---   
FullbackupA.bak 01/01/2013 00:00:00   
>  DifferntialbackupA.bak 02/01/2013 00:00:00 
FullbackupCOPY_ONLYA.bak 02/01/2013 00:00:00
>     TransactionbackupA.trn 02/01/2013 01:00:00
>     TransactionbackupB.trn 02/01/2013 02:00:00
>     TransactionbackupC.trn 02/01/2013 03:00:00
>  DifferntialbackupB.bak 03/01/2013 00:00:00 
FullbackupCOPY_ONLYB.bak 03/01/2013 00:00:00
>     TransactionbackupD.trn 03/01/2013 01:00:00
>     TransactionbackupE.trn 03/01/2013 02:00:00
>     TransactionbackupF.trn 03/01/2013 03:00:00
>  DifferntialbackupC.bak 04/01/2013 00:00:00 
FullbackupCOPY_ONLYC.bak 04/01/2013 00:00:00
>     TransactionbackupG.trn 04/01/2013 01:00:00
>     TransactionbackupH.trn 04/01/2013 02:00:00
>     TransactionbackupI.trn 04/01/2013 03:00:00

Maybe this whole setup is not reasonable I am fairly new to SQL Server and am trying to learn as I go. Any advice/help would be appreciated.

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2 Answers 2

Reset to default
15

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.

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  • I was looking for information on whether you could apply a transaction log to a copy_only full backup. This is really good information!
    – Brain2000
    Nov 19, 2018 at 18:10
2

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.

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