I am using the SQL script on Select SQL Server database size in order to monitor how much my database file usage increased. I am particularly inspecting the "data_used_size" and "log_used_size" fields. But I notice that while the data file usage consistently increases after a set of activities, log file usage sometimes increases and sometimes decreases, thus always staying at a certain level. Why is this?
This is documented in MSDN article about Transaction Log
If the DB is using simple recovery model, after a checkpoint
If full recovery model or bulk-logged recovery model is used, then after a log backup.
Related
I have a database with log file size of 700 MB. Now I have fixed its max file size to 1 GB.
When it reaches 1 GB,transaction failed the reason for the same is that "The transaction log for database is full. To find out why space in the log cannot be reused, see the log_reuse_wait_desc column in sys.databases"
This is same case if I uncheck Autogrowth for log file.
When I checked log_reuse_wait_desc column in sys.databases it says "Active_Transaction".
I am not able to understand why Sql server is not maintaining the max file size limit.Why it cannot delete old logs or something like that to maintain the max file size.
How does it work.
What I want is to limit the log file size that not to exceed 1 GB in any case.
There are a few things you need to consider here, especially if you want to restrict the log file size to 1GB.
as already mentioned, you need to understand the difference
between the three recovery models. Taking log backups is a key task
when using the full recovery model. However this is only part of the
problem; log backups only truncate the inactive part of the log,
therefore a transaction could fill the log file with 1GB+ of data,
and then you are in the same position you are in now... even if you are in simple recovery model (a log backup will not help you here!).
In an ideal situation, you would not restrict the log file in such a way, because of this problem. if possible you want to allow it to auto-grow so, in theory, it could fill the disk.
Transaction log management is a science in itself. Kimberly Tripp has some very good advice on how to manage transaction log throughput here
understanding VLF's will allow you to better manage your transaction log, and could help towards better proportioning your log file for large transactions.
If, after everything you have read, you are still required to limit the transaction log growth, then you will need to consider batch updating large result sets. this will allow you to update, say, 1000 rows at a time, meaning that only 1000 records are written to the log. SQL Server uses write-ahead logging, so in order to complete a transaction, you first need to have enough space in the transaction log to write all the details. If using a simple recovery model, this write-ahead logging is automatically truncated, meaning you don't need to backup the log. Therefore, writing 1000 records at a time (for example) will causing less of a problem than a huge 1,000,000 record insert (say)
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EDIT:
P.s. I've just read your comment above... If you are in full recovery model you MUST do log backups, otherwise sql server WILL NOT recover the space from the log, and will continue to write to the log causing it to expand! However note, you MUST have a full backup for transaction log backups to take effect. SQL Server cannot backup the log if it doesn't have an initial restore point (i.e. the full backup).
I had very large data in database(log) after deleting all the records in the database tables but the database size is not reduced , specially Log File(s) Ldf
ROWS 56274.125000 55306.625000
LOG 179705.437500 179567.046875
how i reduce the size ?
Is the database in Full Recovery Model? If so, you will need to implement Transaction log backups before you can shrink the log-file size.
If you do not need transaction log backups (in case your full backup is taken often enough that the business is okay with losing the amount of data since the previous backup), you can switch the database to run in Simple recovery model.
You can find out which recovery model a database is in by right-clicking the database, selecting "Properties", and then checking the "Options" tab.
You can change the recovery model at that location, too. However, before you do, I highly recommend you to read up on the different recovery models, and the implications of changing them.
When you are ready to change the recovery model, you might want to read this first.
I have a SQL Server database with one log file and it is growing very fast.
But it is happening after I shrink the file before that it was good.
My database recovery model is FULL recovery.
Please help with it.
Assuming you meant transaction log...
If you use FULL recovery model,
to reclaim a space in the transaction logs or shrink it, the log (or database) should be backed up first. If you use also CDC or Replication, even backup is not enough. The space can be reclaimed only after Log Reader Agent read the transaction logs.
The transaction log is growing fast if there are many DB changes.
It sounds like the log file was appropriately sized for your traffic before you shrank it. To paraphrase Elsa from the movie Frozen "Let it grow!". That is, unless you had an event that you can point to that made the it much larger than it typically is, the log file will likely be appropriately sized given your transactional volume.
Oracle has SQL commands that one can issue so that a transaction does not get logged. Is there something similar for SQL Server 2008?
My scenario: We need Tx logs on servers (Dev, QA, Prod), but maybe we can do without them on developer machines.
You can't do without transaction logs in SQL Server, under any circumstances. The engine simply won't function.
You CAN set your recovery model to SIMPLE on your dev machines - that will prevent transaction log bloating when tran log backups aren't done.
ALTER DATABASE MyDB SET RECOVERY SIMPLE;
There is a third recovery mode not mentioned above. The recovery mode ultimately determines how large the LDF files become and how ofter they are written to. In cases where you are going to be doing any type of bulk inserts, you should set the DB to be in "BULK/LOGGED". This makes bulk inserts move speedily along and can be changed on the fly.
To do so,
USE master ;
ALTER DATABASE model SET RECOVERY BULK_LOGGED ;
To change it back:
USE master ;
ALTER DATABASE model SET RECOVERY FULL ;
In the spirit of adding to the conversation about why someone would not want an LDF, I add this: We do multi-dimensional modelling. Essentially we use the DB as a large store of variables that are processed in bulk using external programs. We do not EVER require rollbacks. If we could get a performance boost by turning of ALL logging, we'd take it in a heart beat.
SQL Server requires a transaction log in order to function.
That said there are two modes of operation for the transaction log:
Simple
Full
In Full mode the transaction log keeps growing until you back up the database. In Simple mode: space in the transaction log is 'recycled' every Checkpoint.
Very few people have a need to run their databases in the Full recovery model. The only point in using the Full model is if you want to backup the database multiple times per day, and backing up the whole database takes too long - so you just backup the transaction log.
The transaction log keeps growing all day, and you keep backing just it up. That night you do your full backup, and SQL Server then truncates the transaction log, begins to reuse the space allocated in the transaction log file.
If you only ever do full database backups, you don't want the Full recovery mode.
What's your problem with Tx logs? They grow? Then just set truncate on checkpoint option.
From Microsoft documentation:
In SQL Server 2000 or in SQL Server
2005, the "Simple" recovery model is
equivalent to "truncate log on
checkpoint" in earlier versions of SQL
Server. If the transaction log is
truncated every time a checkpoint is
performed on the server, this prevents
you from using the log for database
recovery. You can only use full
database backups to restore your data.
Backups of the transaction log are
disabled when the "Simple" recovery
model is used.
If this is only for dev machines in order to save space then just go with simple recovery mode and you’ll be doing fine.
On production machines though I’d strongly recommend that you keep the databases in full recovery mode. This will ensure you can do point in time recovery if needed.
Also – having databases in full recovery mode can help you to undo accidental updates and deletes by reading transaction log. See below or more details.
How can I rollback an UPDATE query in SQL server 2005?
Read the log file (*.LDF) in sql server 2008
If space is an issue on production machines then just create frequent transaction log backups.
I read some Books Online about recovery/backup, one stupid question, if I use full database backup/full recovery model, for backup operation itself, will it generate any additional transaction log to source database server? Will full recovery operation generate additional transaction log to destination database?
A more useful view of this might be to say that Full Recovery prevents the contents of the transaction log from being overwritten without some other action allowing them to be overwritten
SQL Server will log most transactions (e.g. bulk load and a few others aside) and when running in simple recovery mode, effectively discard the newly created log contents at the end of the transaction associated with the creation of the same. When running in Full Recovery mode the contents of the trans log are retained until marked as available to be overwritten. To mark them as available to be overwritten one normally performs a backup (either Full or Trans Log).
If there is no space in the trans log and no logs contents marked as available to be overwritten then SQL Server will attempt to increase the size of the logs.
In practical terms Full Recovery requires you to manage your transaction logs, generally by performing a trans log backup every so often (every 1 hour is probably a good rule of thumb if you have no SLA to work to or other driver to determine how often to do this)
I'm not sure I completely understand your question, but here goes. Keeping your DB in Full Recovery mode can make your transaction logs grow to be very large. The trade off is that you can restore to the point of recovery.
The reason that the transaction logs are larger than normal is ALL transactions are fully logged. This can include bulk-logged operations, index creation, etc.
If drive space is not a concern (and with drives being so inexpensive, it shouldn't be), this is the recommended backup approach.