October 5, 2005 at 8:56 am
All,
Check out this result from DBCC SHOWCONTIG.
DBCC SHOWCONTIG scanning 'PATIENTS' table...
Table: 'PATIENTS' (301608513); index ID: 1, database ID: 8
TABLE level scan performed.
- Pages Scanned................................: 2925
- Extents Scanned..............................: 375
- Extent Switches..............................: 378
- Avg. Pages per Extent........................: 7.8
- Scan Density [Best Count:Actual Count].......: 96.57% [366:379]
- Logical Scan Fragmentation ..................: 0.62%
- Extent Scan Fragmentation ...................: 79.20%
- Avg. Bytes Free per Page.....................: 364.0
- Avg. Page Density (full).....................: 95.50%
DBCC execution completed. If DBCC printed error messages, contact your system administrator.
I'm happy with Scan Density, Avg. Page Density, and Logical Scan Fragmentation. But I am confused with the near 80% for Extent Scan Fragmentation.
Any thoughts on this?
Clive
October 6, 2005 at 4:56 am
Having a quick look around this seems to indicate that you have external fragmentation in the extents.
I'm assuming that you have a clustered index on the table? because this doesn't apply to heaps (love that name).
You should also be aware that If you're using INDEXDEFRAG to get rid of some of your fragmentation without causing blocking that this can cause extent fragmentation.
I'd consider looking at doing a full reindex to see if that reduces it, after that consider looking at the fill factor and deciding if it's worth changing it.
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