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Basuc question about High Availability solution. Expand / Collapse
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Posted Monday, September 17, 2012 12:06 AM
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Hi,

I am very new to the DBA scenarios, i am learning the things from the Online stuff.

For high availability solution:
1. We need to take the full backup.
2. We need to take the T-Log backup.

My Question is:

Is full backup doesn't contains the Log backup (As per my knowledge full backup takes the Transaction log also.)? If yes what is the use of taking again T-Log backups.

Please provide info on these basic questions.

Thanks,


Post #1359979
Posted Monday, September 17, 2012 1:18 AM


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SQL* (9/17/2012)
Hi,

I am very new to the DBA scenarios, i am learning the things from the Online stuff.

For high availability solution:
1. We need to take the full backup.
2. We need to take the T-Log backup.

My Question is:

Is full backup doesn't contains the Log backup (As per my knowledge full backup takes the Transaction log also.)? If yes what is the use of taking again T-Log backups.

Please provide info on these basic questions.

Thanks,

I'm assuming you're referring to backup regimes is this correct?

Full backups will form the base of your recovery solution with logs and\or differentials to bring databases up to a set point in time


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Post #1360003
Posted Monday, September 17, 2012 4:24 AM


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Full backups do not contain the transaction logs. That's a myth. A full backup has a complete copy of the database including all completed transactions up to the point of the backup. Any incomplete transactions are cleaned up as part of the restore process.

The thing is, a full backup, depending on the size of your system, can take quite a while and will use some system resources. So you can't run a full backup every 1/2 hour on most production systems. Instead, other backups are used in combination to protect the data in a more granular fashion. That's what log backups are for. They backup just the transaction log. This allows for very fast, lightweight backups, and, as was already mentioned, the ability to restore to a specific point in time. A full backup can only be restored to when it occurred. Logs can be restored to specific moments.

Backups are not a technology problem. They're a business problem. Talk to your business and find out exactly how much time they can afford to lose on the database. If that number is small, you're going to need to work on setting up a recovery mechanism that covers the business adequately.


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Post #1360078
Posted Monday, September 17, 2012 5:18 AM
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Thank you,

I have read in blogs/books that, when we are setting up mirroring/Log shipping we have to take the both Full backup&Transactional backup and restore them to the secondary server as an initial step.

If the Full backup contains all the completed transactions then what is the benefit of again taking the Transactional backup again?

Even if we take the t-log if that contains not completed transactions those will not be committed over secondary right?


Kindly explain.


Post #1360112
Posted Monday, September 17, 2012 6:13 AM


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Because you have to take an initial transaction log backup to begin that process. You're setting up log shipping. It requires you to have logs to ship. The log being referred to is the transaction log. The way you back it up, is the transaction log backup.

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Post #1360136
Posted Monday, September 17, 2012 6:19 AM
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That means, with out Transaction log (Only with the Full Backup) the log shipping and Mirroring will not work.

I could have try but i need to get the confirmation form the experts. I have not find any information related to this question.

Thank you for your time.


Post #1360140
Posted Monday, September 17, 2012 6:35 AM


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SQL* (9/17/2012)
I have read in blogs/books that, when we are setting up mirroring/Log shipping we have to take the both Full backup&Transactional backup and restore them to the secondary server as an initial step.

That's Database Mirroring, Log shipping doesn't require you to take at least one log backup, you only need to initialise the secondary database from a full backup of the primary or let the Log Shpping wizard do this for you.

Furthermore, for mirroring Books Online goes on to say the following

Books Online
Typically, at least one log backup must be taken on the principal database, copied to the mirror server, and restored on the mirror database (using WITH NORECOVERY). However, a log backup might be unnecessary, if the database has just been created and no log backup has been taken yet, or if the recovery model has just been changed from SIMPLE to FULL.


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Post #1360152
Posted Monday, September 17, 2012 6:46 AM
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However, a log backup might be unnecessary, if the database has just been created and no log backup has been taken yet, or if the recovery model has just been changed from SIMPLE to FULL


Is there any specific reason on this restriction?



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