February 11, 2016 at 11:12 pm
Thank you, nice easy question for a Friday, spent ages looking for a trick question!
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February 11, 2016 at 11:50 pm
This was removed by the editor as SPAM
February 12, 2016 at 6:52 am
I was confused by the transaction logs being "from midnight on". What is that relative to? :angry:
February 12, 2016 at 7:10 am
sestell1 (2/12/2016)
I was confused by the transaction logs being "from midnight on". What is that relative to? :angry:
My comment also. I was thinking you stopped transaction logs when the diff was taken then started at midnight.
February 12, 2016 at 7:46 am
I read that as there is a gap of 4 hours with transaction log backups between 8pm and midnight each day. I don't understand from the question how there is a transaction log backup from 9pm. Am I missing something or do I just need more coffee?
My understanding of this question would be this:
1) Restore the full backup from Monday
2) Restore the differential backup from Friday night at 8pm
3) - there are no transaction log backups taken since before the last differential so that is the best I can do.
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February 12, 2016 at 7:50 am
djj (2/12/2016)
sestell1 (2/12/2016)
I was confused by the transaction logs being "from midnight on". What is that relative to? :angry:My comment also. I was thinking you stopped transaction logs when the diff was taken then started at midnight.
Unless the activity of the server fully stops. Why would someone do that? Even if it does, there's no reason to stop them.
When I read from midnight on, I understood that they started at a certain midnight and kept running every 15 minutes. That way we know they're running on HH:00, HH:15, HH:30 & HH:45. That's why mentioning midnight is relevant.
February 12, 2016 at 7:58 am
Luis Cazares (2/12/2016)
djj (2/12/2016)
sestell1 (2/12/2016)
I was confused by the transaction logs being "from midnight on". What is that relative to? :angry:My comment also. I was thinking you stopped transaction logs when the diff was taken then started at midnight.
Unless the activity of the server fully stops. Why would someone do that? Even if it does, there's no reason to stop them.
When I read from midnight on, I understood that they started at a certain midnight and kept running every 15 minutes. That way we know they're running on HH:00, HH:15, HH:30 & HH:45. That's why mentioning midnight is relevant.
I would never do that in a real system but it seems he was not the only person to read it that way. Not a big deal to be honest. My QOTD history is far from unblemished, points mean nothing and the learning and subsequent discussion is happening.
This is an excellent question!!!
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February 12, 2016 at 8:54 am
As I understand it, the transaction log backup at 8pm will contain transaction log records from when the previous transaction log backup was taken (7:45pm) until 8pm. So if you restore the differential backup from 8pm, there's no point restoring the log backup from 8pm, you could start from the one taken at 8:15pm. Is that right?
We take transaction log backups at different times to database backups, so I've never come across this in practice.
February 12, 2016 at 9:12 am
I read this the same way as a lot of others. I wouldn't set up transaction logs to go from midnight until 8:00 pm but I've learned not to read things into questions that are not stated in the question. This was kind of vague.
-Tom
February 12, 2016 at 9:15 am
From midnight on. As in, these are ongoing. I'm not sure why wouldn't think that log backups occur every 15 minutes, on every hour of every day. So 96 times a week.
The RPO is from the last log backup. I had to give a reference time of midnight, so you know that log backups are on the :00, :15, :30, :45 each hour.
February 12, 2016 at 9:22 am
Easy Peasy. Thanks.
February 12, 2016 at 9:23 am
Eh, the "starting at" didn't strike me as that odd, since that's the same language Agent job schedules use.
Also, if we're trying to read the question exactly, it didn't say "Every 15 minutes, from midnight until 8 PM". It said "Every 15 minutes, from midnight on."
Without an ending time specified, that would just mean that starting at midnight, a log backup is taken every fifteen minutes, period. To assume it stopped at 8 PM would be just that, an assumption that goes beyond anything stated in the question.
I think I can understand how that assumption might naturally get made; still, I think the question is fine as it stands.
Of course, in this case my reading turned out to coincide with the solution marked as the correct one, so I may be a bit biased 🙂
Cheers!
February 12, 2016 at 11:53 pm
From the answer section, it says - "Restore the differential backup from Friday night at 8pm".
I have one doubt - do we have to install the diff-backup of just Friday's or the diff- backup from Tuesday's to Friday's?
ww; Raghu
--
The first and the hardest SQL statement I have wrote- "select * from customers" - and I was happy and felt smart.
February 13, 2016 at 2:41 am
Raghavendra Mudugal (2/12/2016)
From the answer section, it says - "Restore the differential backup from Friday night at 8pm".I have one doubt - do we have to install the diff-backup of just Friday's or the diff- backup from Tuesday's to Friday's?
Just Friday.
For backups, two terms have a more or less standardized meaning: "incremental" (includes all changes since the last full or last incremental), and "differential" (includes all changes since the last full).
Differentials grow larger over time - the differential on Friday includes a lot more changes than the one on Monday. But you only need to restore the last so it's less hassle when restoring.
Incrementals have a more or less equal size (if we assume that a day of work always causes approximately the same amount of change in the database), but you need to restore all of them in sequence.
(One could argue that transaction log backups are incremental. They are incremental in nature, when looking at size and restore requirements, but I would not call them that because the methods used for backuping up the data and restoring are completely different from those of a traditional incremental backup).
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