Seeing that the recovery model is set to simple and msdn states that the simple recovery model does not support point-in-time recovery - Does this mean that I won't be able to use my transaction log backups to restore the database in a disaster to an hour before it happened?
Even taking a transaction log backup is not supported for databases using the SIMPLE recovery model. This is a restriction of the database engine based on how this recovery model works, and the recovery features it doesn't support, as you mentioned.
A transaction log backup maintenance plan task automatically skips databases in SIMPLE recovery to avoid causing errors.
Which backup should be done first, the database backup or the transaction log backups? Articles that I'm busy reading say I should do the database backup first and then the transaction log backup else I will get maintenance plan errors, but I'm currently first backing up my transaction logs and then data databases and I'm not getting any errors.
For the reasons I mentioned above, it won't matter for databases using SIMPLE recovery, as they will be skipped by the transaction log backup task.
For databases in the other two recovery models, a full backup must exist before you start taking transaction log backups (just the first time), or you will get an error -- this is probably what the articles refer to.
Point-in-time recovery ability is normally driven by business need -- in other words, you determine how critical the data is and how much you can afford to lose, then set the appropriate recovery model to meet those needs, and finally create a backup solution.
Even though SIMPLE recovery does not support point-in-time recovery, if an hour of data loss is okay, perhaps a differential backup solution could work for you. (There are far too many variables that go into developing this kind of solution to give you a complete picture with what was provided in the question.)
It sounds like you've got a huge transaction that has remained open which has done a lot of work. Run DBCC OPENTRAN on the database and see how long the oldest transaction has been open for. You'll probably need to kill that transaction (or have the user commit if it's someone in Management Studio). Then the log will clear automatically.
Best Answer
Alright, spent yesterday day and night investigating, testing and trying to reproduce the problem. Found the root cause:
MODELdatabase set to theSIMPLErecovery model.If the model database has been set to the
SIMPLErecovery model, and user databases are created withSIMPLErecovery model, SQL Server somehow is treating it as if it is in theFULLrecovery model. Hence waiting forLOG_BACKUPto truncate the log.I have listed the steps in this link to show how I reproduced the problem.
I think the root cause is if a user database was created (not alter after) with simple recovery model, then it has this problem. I blame it on model database as that is the only way to create a user database with the defined recovery model.
This documented in Microsoft Knowledge Base article 2830400 and is fixed in SQL Server 2012 SP1 CU4 and RTM CU7: