Transcation Log filing the entire hdd.

My guess is that your database is in full recovery model and you are not backing up the transaction logs.  Chances are, if you're not backing up the transaction logs currently, you're not concerned about point in time recovery (which is the main point of full recovery model).  If I am correct about not needing point in time recovery, then you'll want to backup the transaction log, change the database to simple recovery model and then shrink the log file.  If you do want point in time recovery, you'll still want to backup the transaction log, shrink the log file, and then set up a backup schedule for backing up your transaction logs in addition to your full backups.

I went back to edit my initial reply but Padawan had replied in the mean time.  

Adding on to the above:
The option to truncate your logfile is a dangerous one.  If you are in the least concerned about point in time recovery, don't do it - it should be a last gasp effort.

If you've got the space on  your backup device, I'd advise running the transaction log backup.  Then you can shrink the log file.

Then, make sure to include transaction log backups as a part of your regular backup cycle.  This marks the space in the log file as reusable so the log file won't grow that large again.

Sorry about that, by the way!  I didn't notice you had posted until after the fact.  Cheers!

>> What is wrong here and how can it be resolved? <<

It depends; most likely it is as described above, but just in case ...

Naturally replace "your_db_name" with your actual db name in the commands below.

1) First, verify that there are no open transactions against the db.

USE your_db_name
DBCC OPENTRAN

2) If you get the expected return message:
"No active open transactions."
    Then run these commands:


USE your_db_name
CHECKPOINT
ALTER DATABASE your_db_name SET RECOVERY SIMPLE
DBCC SHRINKFILE ( 2, 500 )

-- review output from this command to verify that the log file did actually shrink to 500MB
EXEC sp_helpfile

BACKUP DATABASE your_db_name TO DISK = 'x:\full\path\to\full\db\backup\your_db_name.bak'

It might be worth noting that it may take more than one transaction log backup before you see the file shrink, this has to do with the way that the sql logs work. If you would like I can go into more detail, but I think it might be worth just saying, back up your log a couple times before you panic over it not shrinking.

Hi,

First Perform transaction log backup:

backup log  to disk='OS Path.trn'

After performing transaction log backup of database which is having 80 Gb of log files i.e. ldf and after that shrink the log files.

Using SQL management studio
Right click on database
go to task then
go to Shrink then
go to Files

then after that from drop down menu select database log files not data files because Microsoft recommends do not shrink data files i.e. mdf but you can shrink log files i.e. ldf.

OR you can command in sql server :

USE UserDB;
GO
DBCC SHRINKFILE (userdb_log, 7);
GO

After performing above activity once again perform transaction log backup do not worry now log backup size is small and one more time shrink the log files of database and see the results.