Sql-server – Shrink the database only up to its initial size which is set after creating database

maintenanceshrinksql serversql-server-2008-r2

In SQL server every database has a property Initial Size (MB) which can be seen in properties of database in SSMS. By default it will be 3 MB for mdf and 1 MB for ldf file.

So now if create a new database then it will be set to default size(i.e 3 MB for mdf and 1 mb for ldf file).
But after creating the database I change the initial size to some other value say For mdf 10 MB and ldf 5 MB.(In real-time some database administrator may want to change initial after creating database)

But now if shrink the database it will shrink beyond the initial size I have set after creation(consider that no data is there in database otherwise it will shrink to its actual content size). It will shrink till the initial size it had during creation of database(i.e 3mb for mdf and 1 mb for ldf). I was expecting to shrink till the initial size which I have set(i.e 10 mb for mdf and 5mb for ldf). Can it be possible to do? If possible then how?

In some article i saw like dbcc SHRINKFILE can be used to shrink beyond initial size and dbcc SHRINKDATABASE cannot shrink beyond initial size. But I want to shrink only till the initial size to which I have set.

Note: I know that shrink is bad and should not be done.But I want to know how it can be done? If sql server considers only the initial size set during creation of database then what is the use of setting the initial size after creating database?

EDIT:

From microsoft shrink related article:
Using DBCC SHRINKDATABASE you can not shrink database below its initial size.

My question is Can I change the initial size of existing database itself?

EDIT:

I have about 5 sql server instance. All the database where created with default size of 3 mb for data and 1 mb for log(about 3 years back). Now all the databases are in the range of 100-1000 mb. I wont shrink the database normally as it is not good practice. But some database grow more than 10 GB(mdf file itself as i insert so much data in it). So when database is large I will shift unimportant and old contents from this database to another server as it is not required in that server for me. So that database size reduces from 10 GB to 1 GB. Now the remaining 9 Gb left unused. Now I want to specify database size to be reduced to 2 GB so that i will get 1 GB free space(Also 2 Gb is the ideal size for this database), Which can be used to avoid autogrowth till next 1 Gb of data is filled. Also i have set 100 MB auto-growth for this kind of large database which has more writes. So instead of specifying size as 2 GB in shrinkfile command,if it was possible to change initial size to 2 GB (which shrink considers) then it would have been better. During this database creation there was no plan about size ,autogroth etc. As it was created about 3 years back. Now i am planning to set autogrowth etc. I cant again create new database with new initial size and shift data. So I was asking whether I can change the Initial size for existing database?

Best Answer

Initial size is not just 3MB, it is taken from the model database (if not specified during the creation of your user database.) So assuming you haven't specified a initial size during the creation of your user db and you haven't altered the model database file sizes after you have created your userdb you can do the following:

--Create testDB
CREATE DATABASE [TEST_100]
GO


--grow your database file size
ALTER DATABASE [Test] MODIFY FILE ( NAME = N'Test', SIZE = 100MB )
GO


--switch context
USE [TEST_100]
GO



--Find size of modelDB mdf file, this is your initial file size used for the userdb
DECLARE @TargetFileSize int

SELECT  @TargetFileSize = (size * 8 / 1024)
FROM    sys.master_files 
WHERE   database_id = 3 --model database
AND     file_id= 1 --first file is mdf, assuming you have a model with just one mdf. If you have multiple files, change for the one you need to find.


--shrink the the first file of your current database to the target size that you just found.
DBCC SHRINKFILE (1,@TargetFileSize)

EDIT

Okay, some extra info is needed after your edits and comments.

First of all. I feel that the "Initial size" label that you see when you look at the file properties in SSMS is a misnomer. Basically, your intial size is just a concept. It's the first size that is used during creation of the database. You can either explicitly specify this in the CREATE DATABASE statement, or you can have SQL Server implicitly copy it from the model database by ommiting that information during creation.

However, once the database is created, from a DBA perpective there is no such thing as a "initial size" there is only one property visible for a DBA and that is: the actual size. Even the "Initial size" property in SSMS just shows actual size, not the initial size.

Well how come that DBCC SHRINKFILE or DBCC SHRINKDATABASE "know" the initial size then? Even after you have changed the size. Interesting question.

The first page of a dattabase file is the file header page. In there you have, amongst others, 2 properties: size and minsize.

At creation of the file, both file header properties get filled with the inital value:

DBCC TRACEON(3604)
--parameters for DBCC PAGE: (Dbname, fileID, pageID, outputTypeID)
DBCC PAGE('Test_100',1,0,3)with tableresults

enter image description here

Both sizes are in the amount of data pages. In this case. 288 data pages.

Now if I alter the file size:

ALTER DATABASE [test_100] MODIFY FILE ( NAME = N'test', SIZE = 50MB )

enter image description here

You can see that the "size" property is changed to reflect the new size. However, the "MinSize" property still contains the "Initial" size. It's the minimal size to which the shrink command will go.

However, having said all this. I still don't understand why you want to complicate things by first altering the initial size and then shrink to that initial size. Instead of just shrinking directly to a targetsize.

Anyway, to answer your question. The "initial" size is not exposed as a property to the user/dba.

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