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 How does DBCC SHRINKDATABASE work?

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aap
Starting Member

3 Posts

Posted - 2007-10-19 : 03:10:23
Hi,

I'm new here and actually I want to know, how does DBCC SHRINKDATABASE work ?
According to the BOL :
Assume a database named mydb with two data files and two log files. Both data and log files are 10 MB in size. The first data file contains 6 MB of data.
For each file, SQL Server calculates a target size, which is the size to which the file is to be shrunk. When DBCC SHRINKDATABASE is specified with target_percent, SQL Server calculates target size to be the target_percent amount of space free in the file after shrinking. For example, if you specify a target_percent of 25 for shrinking mydb. SQL Server calculates the target size for this file to be 8 MB (6 MB of data plus 2 MB of free space). Therefore, SQL Server moves any data from the last 2 MB of the data file to any free space in the first 8 MB of the data file and then shrinks the file.
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If the size is 10 MB and target_percent is 25, how is the calculation so the final size become 8 MB and the free space become 2 MB ?
I can't understand this section..., so I think I need some explanation about this.
Okay..thanks and I'm waiting for the reply

Kristen
Test

22859 Posts

Posted - 2007-10-19 : 03:24:39
After shrinking the file will be 8MB or which 6MB data and 2MB free space.

The 2MB will be 25% of the total - 2MB of 8MB file is 25%, so when shrinking the Target Percentage is of the file-after-it-has-been-shrunk

Kristen
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aap
Starting Member

3 Posts

Posted - 2007-10-22 : 06:23:23
Okay thanks.
So if I describe, it will be :

Y = 25% * Y + Z
Y = 25 % * Y + 6 MB

Y = Size of File After Shrink
Z = Size of Data
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