July 29, 2007 at 1:14 pm
Folks,
When you run (DBCC Showcontig) most DBA do not understand the outputs such as Pages Scanned, Extents Scanned, Extent Switches, & Avg. Pages per Extent, etc, etc it took me a while to understand it through the help of SQL Server Central. One of the authors’ produced documents explaining the results/outputs of Showcontig and I was wondering if someone could point me to the right location to enable me to produce documentation. Any help will be much appreciated.
Regards,
CEWalden
July 29, 2007 at 10:05 pm
I think it is very important to understand DBCC SHOWCONTIG in SQL2K. Have a read on this topic via the link below. I reckon its good.
http://www.sql-server-performance.com/articles/dba/dt_dbcc_showcontig_p1.aspx
The only thing that I dont really understand about the command is the "Extent Scan Fragmentation". Its correct most of the time, but sometimes, it goes up after DBREINDEX! I've not been able to understand how SQL computes this counter. I've got 8 filegroups in this DB. Not sure if its caused by muptiple filegroups with different sizes allocation.
Simon
DBCC SHOWCONTIG result
DBCC SHOWCONTIG scanning 'xx' table...
Table: 'xx' (21575115); index ID: 1, database ID: 6
TABLE level scan performed.
- Pages Scanned................................: 1060804
- Extents Scanned..............................: 133136
- Extent Switches..............................: 133135
- Avg. Pages per Extent........................: 8.0
- Scan Density [Best Count:Actual Count].......: 99.60% [132601:133136]
- Logical Scan Fragmentation ..................: 0.00%
- Extent Scan Fragmentation ...................: 7.88%
- Avg. Bytes Free per Page.....................: 742.6
- Avg. Page Density (full).....................: 90.83%
DBCC execution completed. If DBCC printed error messages, contact your system administrator.
DBCC SHOWCONTIG scanning 'xx' table...
Table: 'xx' (21575115); index ID: 1, database ID: 6
TABLE level scan performed.
- Pages Scanned................................: 1060804
- Extents Scanned..............................: 133132
- Extent Switches..............................: 133131
- Avg. Pages per Extent........................: 8.0
- Scan Density [Best Count:Actual Count].......: 99.60% [132601:133132]
- Logical Scan Fragmentation ..................: 0.00%
- Extent Scan Fragmentation ...................: 10.60%
- Avg. Bytes Free per Page.....................: 742.6
- Avg. Page Density (full).....................: 90.83%
DBCC execution completed. If DBCC printed error messages, contact your system administrator.
Simon Liew
Microsoft Certified Master: SQL Server 2008
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