If this backup operation keeps running for a long time, the SQL Transaction Log truncation will be delayed for a longer time and the SQL Transaction Log file will grow, due to not being able to reuse the inactive part of the log.
When the SQL Server Transaction Log file of the database runs out of free space, you need first to verify the Transaction Log file size settings and check if it is possible to extend the log file size. If you are not able to extend the log file size and the database recovery model is Full, you can force the log truncation by changing it to Simple recovery model.
If the database recovery model is already Simple or changing it to Simple recovery model is not applicable, you need to identify what is preventing the SQL Server Transaction Log from being truncated. The sys. Other values that may return from the sys. After identifying the reason behind preventing the SQL Transaction Log from being truncated, you can troubleshoot that blocker as discussed earlier in this article. It is always better to be a proactive database administrator and keep an eye on the SQL Server Transaction Log file growth, in order to prevent catastrophic issues when having the log file running out of free space for a long time.
Rather than sleeping beside the server, you can use a monitoring tool such as the System Center Operations Manager SCOM tool, Performance Monitor counters, or simply create an alert that reads from one of the system catalog views and notify an operator by email when the free space of the SQL Transaction Log file becomes under a predefined threshold. The below query can be used to check the free space percentage in the SQL Transaction Log file of the current database:. If the result returned from the previous query falls down a predefined threshold, before running the SQL Server Transaction Log file out of free space, the DBA will be notified by an email, SMS or call based on the monitoring tool used in your entity.
In the next article of this series, we will discuss the different operations that can be performed on the SQL Transaction Log including the back, truncate and shrink operations, and make it easier for the reader to identify one from the other. Stay tuned! Author Recent Posts. Ahmad Yaseen.
Also, he is contributing with his SQL tips in many blogs. View all posts by Ahmad Yaseen. Latest posts by Ahmad Yaseen see all. It may be due to distributor, who is overloaded and have problem in accepting transactions. It may be because of the log reader agent who should run it often. It is somewhat similar to the replication of transaction, which requires that the transaction remain log until record has been written to disk on mirror server.
If the server of mirror instance falls behind the server principal of instance then, the amount of active log space will grow.
In such a case user needs to stop the database mirroring, take a long backup of truncates log by applying that log backup to database of mirror and start the mirroring again. Mirroring of database is somewhat similar to transactional replication, which requires that the transactions should remain in log until all the records are written to disk on mirror server.
If the server of mirror instance falls behind the server of principal instance then, the amount of active log space will grow. In such a case, user needs to stop the mirroring of database by taking a backup of log, which truncated the log, apply that log backup to database of mirror, and start the mirroring again.
After identifying the issue, user is able to truncate the log file, that user needs to shrink the file back to the manageable size. User must avoid file shrinking on consistent basis that can lead to issues of fragmentation. However, they have performed log truncation and requires log file to be smaller. Then user can also do it via a management studio with right click of database, selecting all tasks, shrink, and then select files or database.
It can also be done by using TSQL and running mentioned commands. In addition, the user must check that databases are NOT set to auto-shrink. The databases that are shrink at regular intervals can encounter the problems of real performance. In the above discussion, the problem faced by users of SQL transaction log is growing too big is discussed.
Along with it, the cause and solutions are described. If you shrink the log file to a ridiculously small size, and SQL Server just has to grow it again to accommodate your normal activity, what did you gain? Were you able to make use of that disk space you freed up only temporarily? If you need an immediate fix, then you can run the following:. Otherwise, set an appropriate size and growth rate. As per the example in the point-in-time recovery case, you can use the same code and logic to determine what file size is appropriate and set reasonable autogrowth parameters.
Second, if you are in FULL recovery model, this will destroy your log chain and require a new, full backup. Detach the database, delete the log file, and re-attach. I can't emphasize how dangerous this can be. Your database may not come back up, it may come up as suspect, you may have to revert to a backup if you have one , etc. Use the "shrink database" option. Shrink the log file to 1 MB. This looks tempting because, hey, SQL Server will let me do it in certain scenarios, and look at all the space it frees!
Unless your database is read only and it is, you should mark it as such using ALTER DATABASE , this will absolutely just lead to many unnecessary growth events, as the log has to accommodate current transactions regardless of the recovery model. What is the point of freeing up that space temporarily, just so SQL Server can take it back slowly and painfully? Create a second log file.
This will provide temporarily relief for the drive that has filled your disk, but this is like trying to fix a punctured lung with a band-aid.
You should deal with the problematic log file directly instead of just adding another potential problem. Other than redirecting some transaction log activity to a different drive, a second log file really does nothing for you unlike a second data file , since only one of the files can ever be used at a time. Paul Randal also explains why multiple log files can bite you later.
Instead of shrinking your log file to some small amount and letting it constantly autogrow at a small rate on its own, set it to some reasonably large size one that will accommodate the sum of your largest set of concurrent transactions and set a reasonable autogrow setting as a fallback, so that it doesn't have to grow multiple times to satisfy single transactions and so that it will be relatively rare for it to ever have to grow during normal business operations.
The former is much too small in this day and age, and the latter leads to longer and longer events every time say, your log file is MB, first growth is 50 MB, next growth is 55 MB, next growth is Please don't stop here; while much of the advice you see out there about shrinking log files is inherently bad and even potentially disastrous, there are some people who care more about data integrity than freeing up disk space.
A blog post I wrote in , when I saw a few "here's how to shrink the log file" posts spring up. A blog post Brent Ozar wrote four years ago, pointing to multiple resources, in response to a SQL Server Magazine article that should not have been published. A blog post by Paul Randal explaining why t-log maintenance is important and why you shouldn't shrink your data files, either.
Mike Walsh has a great answer above, of course, covering some of these aspects too, including reasons why you might not be able to shrink your log file immediately. You can also see the content of your log file. This is the most frequently faced issue for almost all the DBAs where the logs grows and fills out the disk. Log backups will help you control the log growth unless there is something that is holding up the logs from being reused.
If you have identified what actually is causing it then try to fix it accordingly as explained in below page. Having proper log backups scheduled is the best way of dealing with log growth unless for an unusual situation. Sign up to join this community.
The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Ask Question. Asked 8 years, 11 months ago. Active 1 year, 11 months ago. Viewed k times. This one seems to be a common question in most forums and all over the web, it is asked here in many formats that typically sound like this: In SQL Server - What are some reasons the transaction log grows so large?
Why is my log file so big? What are some ways to prevent this problem from occurring? What do I do when I get myself on track with the underlying cause and want to put my transaction log file to a healthy size? Improve this question. Community Bot 1. Mike Walsh Mike Walsh Add a comment. Active Oldest Votes. A Shorter Answer: You probably either have a long running transaction running Index maintenance?
Intermission: Recovery in General Before we talk about Recovery Models: let's talk about recovery in general. Recovery Models Onto the recovery models: Simple Recovery Model So with the above introduction, it is easiest to talk about Simple Recovery model first. Switching from Simple to Full has a Gotcha.
There are rules and exceptions here. We'll talk about long running transactions in depth below. Full Recovery Model without log backups is bad. This happens all the time to people. Why is this such a common mistake? This is why it is important to change defaults when they don't work for your organization and its needs Full Recovery Model with too few log backups is bad. How do I find out what log backup frequency I need? You need to consider your log backup frequency with two things in mind: Recovery Needs - This should hopefully be first.
In the event that the drive housing your transaction log goes bad or you get serious corruption that affects your log backup, how much data can be lost? If that number is no more than minutes, then you need to be taking the log backup every minute, end of discussion. Log Growth - If your organization is fine to lose more data because of the ability to easily recreate that day you may be fine to have a log backup much less frequently than 15 minutes.
Maybe your organization is fine with every 4 hours. But you have to look at how many transactions you generate in 4 hours. Will allowing the log to keep growing in those four hours make too large of a log file? Will that mean your log backups take too long?
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