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SQL LOG Size

Posted on 2014-02-05
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Last Modified: 2014-02-05
Hi Experts,

several days ago I have shrinked my logfile for SQL.
Now it is again 50GB. But inside the file 1% is used.

My backup is set with BE 2012.
I have a Full Backup each week.
I have two incremental jobs for DIFFERENTIAL and LOGS.

So why the grows and just 1% is filled ?
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Question by:Eprs_Admin
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Carl Tawn earned 100 total points
ID: 39835179
Probably because it will have had 50GB worth of data in it at some point. The log will grow as it needs to, but it won't automatically shrink back down again.

You need to be monitoring your log size and make sure it is sized appropriately. Generally your log will need to be at least the size of your largest index.
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by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 400 total points
ID: 39835197
to clarify: shrinking the file regularly is not a good practice.
better make sure you are running regularly transaction log backups (if your db is in full recovery mode), and for "big jobs" (doing a lot of data modifications) ensure they are optimized.
for example, if this is a datawarehouse like db, you should consider that this kind of databases typically has nightly jobs which DO require large log files, and shrinking the file (regularly) will require to re-enlarge the file again... just a waste of I/O
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by:Eprs_Admin
ID: 39835287
ok, I have seen in the report nearly 30% of the DB are indexes.
But how to find out how big are the indexes ?
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by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 400 total points
ID: 39835292
30% of the DB being indexes is likely just normal, nothing to worry about.
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Author Comment

by:Eprs_Admin
ID: 39835318
There is another DB on the server .
The MDF file has 20GB and the LDF file has 85GB.
The report cannot find any extensions about the logfile.
The LDF file is used with 0.5%.
But the LDF file has 50% of indexes.
Can I shrink the file with the gui and reorganize the logfile ?
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by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 400 total points
ID: 39835340
>But the LDF file has 50% of indexes.
unless the file has been incorrectly named with .ldf as extension, but actually being a data file, this is not possible.
does the file show up as log file or as data file?
if it's log file, I wonder about that report.
if it's a data file, you might consider to rename the file (but that's another question), and leave otherwise the file alone.

it might be a filegroup implementation, so you can "locate" tables or indexes on dedicated filegroups (and hence files), this to improve I/O performance .
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Author Comment

by:Eprs_Admin
ID: 39835355
The DB has two files.
db.mdf and db.ldf

Strange is , the db.mdf has just 20GB
The db.ldf file has 80GB

And the report of the db shows no growing activity of the db.ldf
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Assisted Solution

by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 400 total points
ID: 39835359
again: the log file may be indeed MUCH larger than the data of the db.
it really depends on the activity on your database.
if you have a HUGE job running, using lots of data transformations / extractions etc, this is perfectly NORMAL.

so, unless you check on those jobs, you cannot "know" if it's normal or not.
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Author Comment

by:Eprs_Admin
ID: 39835384
ok thanks for the infos.
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