Re: Make a backup only if necessary

From	Erland Sommarskog <esquel@sommarskog.se>
Newsgroups	comp.databases.ms-sqlserver
Subject	Re: Make a backup only if necessary
Date	2024-05-27 22:43 +0200
Organization	Erland Sommarskog
Message-ID	<XnsB17FE71C2C3C7Yazorman@127.0.0.1> (permalink)
References	<20240527125929.d701039c2aec3196dc3d4731@g{oogle}mail.com>

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Anton Shepelev (anton.txt@g{oogle}mail.com) writes:
> I am working on an in-house backup solution for our MSSQL
> databases, and have found that a differential backup may
> take considerable space (around 1 Mb) 

I'm tempted to say that 1MB in size for a database back is very small.

> I want to make sure that my differential backups are not
> useless.  One solution is to compare byte-for-byte each new
> diff. backup with the previous one, and delete the copy if
> it turn out redundant, but I wondered if there were a
> simpler method.

To restore a database you need most recent full and most recent diff, 
so keeping both is not really necessary. Unless you would want to 
perform some sort of point-in-time restore. But normally, you use
log backups for that, not diff backups.

In any case, RESTORE HEADERONLY on the backup and checking last LSN 
seems to be like a tenable solution. You could also use sys.fn_dblog
to find the last LSN - but keep in mind that this is an undocumented 
and unsupported function.

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Make a backup only if necessary Anton Shepelev <anton.txt@g{oogle}mail.com> - 2024-05-27 12:59 +0300
  Re: Make a backup only if necessary Anton Shepelev <anton.txt@g{oogle}mail.com> - 2024-05-27 13:53 +0300
  Re: Make a backup only if necessary Erland Sommarskog <esquel@sommarskog.se> - 2024-05-27 22:43 +0200
    Re: Make a backup only if necessary Anton Shepelev <anton.txt@g{oogle}mail.com> - 2024-05-28 12:41 +0300
      Re: Make a backup only if necessary Erland Sommarskog <esquel@sommarskog.se> - 2024-05-28 20:11 +0200
        Re: Make a backup only if necessary Anton Shepelev <anton.txt@gmail.moc> - 2024-05-29 00:52 +0300
          Re: Make a backup only if necessary Anton Shepelev <anton.txt@g{oogle}mail.com> - 2024-05-31 13:53 +0300
            Re: Make a backup only if necessary Erland Sommarskog <esquel@sommarskog.se> - 2024-06-01 11:34 +0200
              Re: Make a backup only if necessary Anton Shepelev <anton.txt@gmail.moc> - 2024-06-02 14:43 +0300
                Re: Make a backup only if necessary Erland Sommarskog <esquel@sommarskog.se> - 2024-06-04 20:22 +0200
                Re: Make a backup only if necessary Anton Shepelev <anton.txt@g{oogle}mail.com> - 2024-06-05 17:15 +0300
                Re: Make a backup only if necessary Anton Shepelev <anton.txt@g{oogle}mail.com> - 2024-06-05 19:37 +0300

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