SQL transactionlog backup promoted to differential backup

Last post 03-14-2019, 4:34 AM by LangeWim. 2 replies.
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  • SQL transactionlog backup promoted to differential backup
    Posted: 03-13-2019, 8:12 AM

    We have a lot of subclients containing SQL databases with a mix of recovery models: simple or full.

    After a full database backup, a transactionlog backup is started:

    • sometimes the simple databases are skipped
    • sometimes simple databases are "promoted for DIFFERENTIAL backup"
    WHAT is causing this difference?? Can I change this behaviour?
    (I do understand that you cannot perform a log backup on a simple database. And no: it is not covered by the 'conversion rules').
  • Re: SQL transactionlog backup promoted to differential backup
    Posted: 03-13-2019, 10:52 AM


    Before v11 SP11 conversion of Transaction log backup to Differential was default behavior. Starting SP11 databases in Simple recovery model are skipped by default during transaction log backup and conversion is not happened. 

    Behavior can be changed by GUI option in control panel or by global parameter or by registry key. So if you have all your clients on the same service pack but some clients still exhibit different behavior, I'd suggest to check if registry key is being set on client. Name of the key you should look for is bSkipTLForSimpleRecoveryModelDB. But as I said, starting SP11 you don't need this key unless you actually want to see differential backup being run for Simple RM databases

  • Re: SQL transactionlog backup promoted to differential backup
    Posted: 03-14-2019, 4:34 AM

    Hi Nadia,

    These where the clues I needed. Thanks!


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