Can I use the "backup" transact sql command (sql-server 2008)
when my database is used (read/write) by other users.
Or I must switch to single_user mode before doing this?
Yes, it will let you do that. There are considerations though, regarding full and precise restoration of the data should a restore operation become necessary.
Best you read up on the whole thing so you can choose the best back-up method for your situation.
Yes, you can use the "backup" T-SQL command even the database is used (read/write) by other users.
For example, you are going to make a full database backup by T-SQL command:
BACKUP DATABASE Test TO DISK ='D:/Test.bak'
Suppose someone is working with the table at this moment. So, the transaction "A" started before the full backup began, made some changes after the checkpoint and committed before the backup completed.
In this case, the full backup includes all transaction log records starting from the latest active transaction. This implies that the full backup includes the whole transaction "A" with all changes that were made after the checkpoint to apply those changes during the database recovery process.
Related
Given a SQL Server 2008 .bak file, is there a way to restore the data file only from the .bak file, without the transaction log?
The reason I'm asking is that the transaction log file size of this database is huge - exceeding the disc space I have readily available.
I have no interest in the transaction log, and no interest in any uncompleted transactions. Normally I would simply shrink the log to zero, once I've restored the database. But that doesn't help when I have insufficient disc space to create the log in the first place.
What I need is a way to tell SQL Server to restore only the data from the .bak file, not the transaction log. Is there any way to do that?
Note that I have no control over the generation of the .bak file - it's from an external source. Shrinking the transaction log before generating the .bak file is not an option.
The transaction log is an integral part of the backup. You can't tell SQL Server to ignore the transaction log, because there is no way to let's say restore and shrink the transaction log file at the same time. However, you can take a look at DBA post to hack the process, although it is not recommended at all
Alternatively you could try some third party tools for restoring, particularly virtual restoring process that can save a lot of space and time. Check out ApexSQL Restore, RedGate Virtual Restore, Idera Virtual Database.
Disclaimer: I work for ApexSQL as support engineer
No, the transaction log is required.
Option 1:
An option may be to restore it to a machine that you DO have enough space on. Then on the restored copy change the logging to either bulk logged or simple, shrink the logs, do another backup operation on this new copy and then use that to restore to the target machine with the now much smaller transaction log.
Option 2:
Alternatively, perhaps the contact at the external source could shrink the transaction log before sending it to you (this may not work if the log is large due to a lot of big transactions).
Docs on the command to shrink the log file are available here.
This is really a question for the ServerFault or DBA sites, but the short answer is no, you can only restore the full .bak file (leaving aside 'exotic' scenarios such as filegroup or piecemeal restores). You don't say what "huge" means, but disk space is cheap; if adding more really isn't an option then you need to find an alternative way of getting the data from your external source.
This may not work since you have no control over the generation of the .bak file, but if you could convince your source to detach the database and then send you a copy of the .mdf file directly, you could then attach the .mdf and your server would automatically create a new empty transaction log file.
See sp_detach_db and sp_attach_db (or CREATE DATABASE database_name FOR ATTACH depending on your sql server version).
I know this is an old thread now, but i stumbled across it while I was having transactional log corruption issues, here is how I got around it without any data loss (I did have down time though!)
Here is what I did:--
Stop the sql server instance service
make a copy of the affected database .mdf file and .ldf file (if you have an .ndf file, copy that as well!) - Just to be sure, you can always put these back if it doesn't work for you.
restart the service.
Log into sql management studio and change the database mode to simple, then take a full backup.
Change the database type back again and once again take a full backup, then take a transactional log backup.
Detach the database.
Right click on databases and click on restore, select the database name from the drop down list, select the later full database backup created (not the one taken from the simple mode) and also select the transactional log backup.
Click restore and it should put it all back without any corruption in the log files.
This worked for me with no errors and my backups all worked correctly afterwards and there were no more transactional log errors.
I understand that the transaction logs keep a record of historical transactions in order to facilitate a restore if needed. However do I need to keep creating transaction log backups for inactive databases that are hanging around on the server? No DDL statements are run against them and they are just used for reference.
I am just a bit worried that I might run out of log space if I get this wrong.
Have you considered changing the recovery model of your databases to the SIMPLE recovery model? Doing so would negate the need to backup the transaction log as it would be automatically re-used in the "unlikely" event that you need it to be.
I would still advise that regular FULL database backups be taken.
Also, if these database are indeed true read only databases then why not consider setting them to be so. This action would have the advantage of immediately highlighting any queries/users that are "still" issuing DML operations when you believe there to be none.
Other options for identifying queries that are performing more than just READ operations include running a Profiler Trace of activity on your database server and also an aggressive option would be to revoke all data modification rights from the relevant database Users.
Transaction logs are actually truncated when they're backed up. So, if these databases are actually inactive, you shouldn't be backing up any transaction logs for them since the logs would be empty.
Also, common practice for "inactive" databases would be to make them READ ONLY with a SIMPLE recovery model.
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 have one database which contains the most recent data, and I want to replicate the database content into some other servers. Due to non-technical reasons, I can not directly use replicate function or sync function to sync to other SQL Server instances.
Now, I have two solutions, and I want to learn the pros and cons for each solution. Thanks!
Solution 1: detach the source database which contains the most recent data, then copy to the destination servers which need the most recent data, and attach database at the destination servers;
Solution 2: make a full backup of source server for the whole database, then copy data to destination servers and take a full recovery at the destination server side.
thanks in advance,
George
The Detach / Attach option is often quicker than performing a backup as it doesn't have to create a new file. Therefore, the time from Server A to Server B is almost purely the file copy time.
The Backup / Restore option allows you to perform a full backup, restore that, then perform a differential backup which means your down time can be reduced between the two.
If it's data replication you're after, does that mean you want the database functional in both locations? In that case, you probably want the backup / restore option as that will leave the current database fully functional.
EDIT: Just to clarify a few points. By downtime I mean that if you're migrating a database from one server to another, you generally will be stopping people using it whilst it's in transit. Therefore, from the "stop" point on Server A up to the "start" point on Server B this could be considered downtime. Otherwise, any actions performed on the database on server A during transit will not be replicated onto server B.
In regards to the "create a new file". If you detach a database you can copy the MDF file immediately. It's already there ready to be copied. However, if you perform a backup, you have to wait for the .BAK file to be created and then move it to it's new location for a restore. Again this all comes down to is this a snapshot copy or a migration.
Backing up and restoring makes much more sense, even if you might eek out a few extra minutes from a detach attach option instead. You have to take the original database offline (disconnect everyone) prior to a detach, and then the db is unavailable until you reattach. You also have to keep track of all of the files, whereas with a backup all of the files are grouped. And with the most recent versions of SQL Server the backups are compressed.
And just to correct something: DB backups and differential backups do not truncate the log, and do not break the log chain.
In addition, the COPY_ONLY functionality only matters for the differential base, not for the LOG. All log backups can be applied in sequence from any backup assuming there was no break in the log chain. There is a slight difference with the archive point, but I can't see where that matters.
Solution 2 would be my choice... Primarily becuase it won't create any downtime on the source database. The only disadvatage i can see is that depending on the database recovery model, the transaction log will be truncated meaning if you wanted to restore any data from the transaction log you'd be stuffed, you'd have to use your backup file.
EDIT: Found a nice link; http://sql-server-performance.com/Community/forums/p/5838/35573.aspx
So our SQL Server 2000 is giving me the error, "The log file for database is full. Back up the transaction log for the database to free up some log space."
How do I go about fixing this without deleting the log like some other sites have mentioned?
Additional Info: Enable AutoGrowth is enabled growing by 10% and is restricted to 40MB.
To just empty it:
backup log <dbname> with truncate_only
To save it somewhere:
backup log <dbname> to disk='c:\somefile.bak'
If you dont really need transactional history, try setting the database recovery mode to simple.
Scott, as you guessed: truncating the log is a bad move if you care about your data.
The following, free, videos will help you see exactly what's going on and will show you how to fix the problem without truncating the logs. (These videos also explain why that's such a dangerous hack and why you are right to look for another solution.)
SQL Server Backups Demystified
SQL Server Logging Essentials
Understanding Backup Options
Together these videos will help you understand exactly what's going on and will show you whether you want to switch to SIMPLE recovery, or look into actually changing your backup routines. There are also some additional 'how-to' videos that will show you exactly how to set up your backups to ensure availability while managing log file sizing and growth.
ether backup your database logs regularly if you need to recover up to the minute or do other fun stuff like log shipping in the future, or set the database to simple mode and shrink the data file.
DO NOT copy, rename, or delete the .ldf file this will break your database and after you recover from this you may have data in an inconsistent state making it invalid.
I don't think renaming or moving the log file will work while the database is online.
Easiest thing to do, IMO, is to open the properties for the database and switch it to Simple Recovery Model. then shrink the database and then go back and set the DB to Full Recoery Model (or whatever model you need).
Changing the logging mode forces SQL Server to set a checkpoint in the database, after which shrinking the database will free up the excess space.
My friend who faced this error in the past recommends:
Try
Backing up the DB. The maintenance plan includes truncation of these files.
Also try changing the 'recovery mode' for the DB to Simple (instead of Full for instance)
Cause:
The transaction log swells up due to events being logged (Maybe you have a number of transactions failing and being rolled back.. or a sudden peaking in transactions on the server )
You may want to check related SO question:
How do you clear the transaction log in a SQL Server 2005 database?
Well you could take a copy of the transaction log, then truncate the log file, which is what the error message suggests.
If disk space is full and you can't copy the log to another machine over the network, then connect a drive via USB and copy it off that way.
You have the answer in your question: Backup the log, then it will be shrunk.
Make a maintenance plan to regularly backup the database and don't forget to select "Backup the transaction log". That way you'll keep it small.
If it's a non production environment use
dump tran <db_name> with no_log;
Once this has completed shrink the log file to free up disk space. Finally switch database recovery mode to simple.
As soon as you take a full backup of the database, and the database is not using the Simple recovery model, SQL Server keeps a complete record of all transactions ever performed on the database. It does this so that in the event of a catastrophic failure where you lose the data file, you can restore to the point of failure by backing up the log and, once you have restored an old data backup, restore the log to replay the lost transactions.
To prevent this building up, you must back up the transaction log. Or, you can break the chain at the current point using the TRUNCATE_ONLY or NO_LOG options of BACKUP LOG.
If you don't need this feature, set the recovery model to Simple.
My dear friend it is vey important for a DBA to check his log file quite frequently. Because if you don't give much attention towards it some day it is going to give this error.
For this purpose you have to periodically take back up so that the logs file would not faced such error.
Other then this the above given suggestion are quite right.
Rename it it. eg:
old-log-16-09-08.log
Then the SQL server can use a new empty one.