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Database Snapshots Expand / Collapse
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Posted Thursday, December 18, 2008 10:23 AM
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A database snapshot cannot be backed up, either with SSMS or any third party software that I'm aware of. Technically since a db snapshot is viewed as a read-only database, a third party software could read the database and create it's own backup file... but it cannot use the SQL backup agents.

A Snapshot Backup is a not a database snapshot in the sense CREATE DATABASE ... AS SNAPSHOT, instead it's a method supported by SQL Server for performing database backups.

As BOL states the full, partial or file backup types can utilize this method for backing up a database. You are not performing a full/partial/file backup against a database snapshot created by the DDL statement.

David



Post #622296
Posted Thursday, December 18, 2008 11:45 PM
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Thanks for your thoughts! The intent of the question was not to challenge you SQL Gurus, it was a "trick" question in fact to gain more thoughts from you all.
Post #622618
Posted Friday, December 19, 2008 9:18 AM


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Raghu

Agreed your question did excellently perform the task of teaching. Spent a lot of time with BOL and Technet,+ MSDN and perhaps learned more than what I wanted to know, but teach me something new - YES


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Post #623100
Posted Sunday, December 21, 2008 2:07 AM
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Nice question...


Post #623549
Posted Monday, June 7, 2010 11:01 PM
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Nice question, at least in it's current form.
Post #933790
Posted Wednesday, September 1, 2010 1:26 AM
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I also beileve, beetr take a fresh snaphot

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Post #978539
Posted Tuesday, December 7, 2010 10:13 AM


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Brian LeBlanc-449582 (12/18/2008)
The premise of the question seemed to be “how to reduce the size of the snapshot?” and the answer is – Take another snapshot. I agree this is a crappy question…If a DBA came up to this scenario and was asked to reduce the size of the snapshop file by doing a backup and he replied “you can’t backup a Snapshot” and walked away, I would fire them. I would expect the DBA to say “I’ll take care of it” and do another snapshot to reduce the size.


I would expect the DBA to ask whether the snapshot was still required (because reports or other queries against the state of play as at that snapshot date were still needed) not to go off and replace the snapshot with a new one (and effectively make it impossible or at least very expensive to run those required queries and/or generate those required reports). I would also expect him to think I was an idiot for having raised the issue - if that snapshot was no longer required for report generation or ad hoc queries it should have been deleted already, so that its size would be irrelevant.

It's a good question not a crappy one, it rewuires you to think outside the narrow tecnhical box and consider real business needs.

Of course I intensely dislike the explanation, which doesn't attempt to explain why "take another snapshot" (as opposed to "delete the snapshot because it's obsolete") can never be the right answer (you might want to do that, but not because this one is too big, only because there is a frozen state you want to be able to run queries against and this snapshot doesn't represnt that state).


Tom
Post #1031373
Posted Tuesday, December 7, 2010 10:25 AM


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bitbucket-25253 (12/18/2008)
Webrunner
It helped me, in the sense that I was reminded that you can't take a backup of a snapshot


I suggest you go to BOL (The link is in my previous post), which says you can backup a snapshot. True it is 3rd party software, but SQL 2005 contains built in specific capability to allow the 3rd party software to perform a back up of a snapshot.

So can a snapshot be backed up or not. Certainly not using SSMS or other SQL tools generally available to a DBA, but it can be backed up..

No, a snapshot can't be backed up.

A snapshot backup of a database is not a backup of a database snapshot, it's yet another backup[ mechanism and yet another differnet use of the word "snapshot" (to go alongside database snapshot and replication snapshot) and yet another useul point-in-time view of a database (to go alongside database snapshot and shared scalable database).

When I say a database snapshot can't be backed up, I don't mean that it's impossible to take a copy of the sparse data (by splitting a mirror or whatever means you like) but I do mean that that copy is NOT a backup from which you can ever restore the snapshot database, ie it's not a backup at all.


Tom
Post #1031386
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