DBCC SHRINKDATABASE TRUNCATEONLY - 2008R2 vs 2012
TRUNCATEONLY affects both the LOG and the DATA files in 2008. On BOL for SQL Server 2012 the message simply indicates that if you only wish to SHRINK the database file, then you should use DBCC SHRINKFILE which will allow you to shrink either the data or log files.
For 2008, it is clearly indicated that TRUNCATEONLY only affects DATA files.
Lets test. To visualize what happens using TRUNCATEONLY
with SHRINKDATABASE
, here is a run down of what happened to a database called performance
that I have installed locally.
SELECT @@VERSION;
Microsoft SQL Server 2008 R2 (SP2) - 10.50.4000.0 (X64)
Jun 28 2012 08:36:30
Copyright (c) Microsoft Corporation
Enterprise Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1)
USE performance;
I ran DBCC LOGINFO
just to take a peak inside the transaction log and found that all of the virtual log files after about 200 were inactive, status = 0. In my performance database, all those inactive VLFs can be truncated and the space can be given back to the OS.
Here is some sample output from LOGINFO.
FileId FileSize StartOffset FSeqNo Status Parity CreateLSN
------ -------- ----------- ------ ------ ------ -----------------
2 253952 8192 23 2 64 0
2 253952 262144 24 2 64 0
2 270336 516096 25 2 64 24000000013400005
I then ran DBCC SQLPERF(LOGSPACE)
and got the following output
DBCC SQLPERF(LOGSPACE)
/*
Database Name Log Size (MB) Log Space Used (%) Status
Performance 9870,867 3,395626 0
*/
I then ran
DBCC SHRINKDATABASE(PERFORMANCE, truncateonly)
and got the following result
/*
DbId FileId CurrentSize MinimumSize UsedPages EstimatedPages
8 1 66464 288 44944 44944
8 2 116584 72 116584 72
*/
Next, I reran
DBCC SQLPERF(LOGSPACE)
and got
/*
Database Name Log Size (MB) Log Space Used (%) Status
Performance 910,8047 37,08699 0
*/
SHRINKDATABASE
with TRUNCATEONLY
gave back over 9 GB of available space from the transaction log file back to the OS.
I tried the same experiment with another database called performance2
sp_spaceused
/*
Performance2 52.19 MB 22.81 MB
*/
DBCC SHRINKDATABASE(Performance2, truncateonly)
sp_spaceused
/*
database_name database_size unallocated space
Performance2 31.13 MB 21.13 MB
*/
Which gave back 20 MB to the OS. Using SQL Server 2008, SHRINKDATABASE TRUNCATEONLY
shrinks both data and transaction log files.
I just tested with a scratch database, and using the TRUNCATEONLY option caused both the data file and log file to be shrunk.
I believe what they're trying to clarify is that the TRUNCATEONLY option changes the behavior when shrinking the data file (i.e. don't rearrange any data pages, just chop off the unused space at the end), but the log file will still be shrunk normally.
If my understanding of the option is correct, then this is probably a better way to describe it:
The log file will still be shrunk normally when using the TRUNCATEONLY option. This option only affects the behavior when shrinking data files. To truncate only the data file, use DBCC SHRINKFILE.