Checkpoints

• Karim Hemani

  SSCrazy

  Points: 2063

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  January 2, 2006 at 12:17 am

  #111128

  Hi,

  There are a couple of questions I have that I would appreciate your help with:

  • Does SQL Server suspend all active transactions when it is processing a checkpoint.
  • BOL states that the truncation point for the transaction log is the earlier of the most recent checkpoint and the start of the oldest active transaction. But isn't it the start of the oldest active transaction in both cases, the reasoning being as follows. When the transaction log contains records for active transactions before the most recent checkpoint, the truncation point will be the start of the oldest active transaction. The other scenario is when there are no active transactions at the most recent checkpoint. In such a case, the truncation point will once again be the start of the oldest active transaction since there would be nothing in between the most recent checkpoint and the start of the oldest active transaction.

  Please clarify.

  Thanks,

  Karim

• Steve Jones - SSC Editor

  SSC Guru

  Points: 736568

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  January 2, 2006 at 9:02 am

  #612302

  No idea if transactions are suspended, but I don't think so. Haven't seen significant slowdowns during log backups.

  The start would be the last checkpoint if there are no active transactions, just inactive (committed) ones.