There a way to quantify how much query performance will suffer once an index becomes heavily fragmented? I have a client with a 365x24x7 system that suffers from locking/blocking during index optimizations, so they are considering reducing the frequency or doing away with index optimizations altogether for specific indexes. I knew that this is a good idea, so I’d like to be able to quantify the performance impct that would result.

create table #frag(
tabName varchar(200)
)
insert into #frag
select S.name + ‘.’ + tbl.[name] TableName
from sys.dm_db_index_physical_stats (null, null, null, null, null )as mn
inner join sys.tables tbl on tbl.[object_id] = mn.[object_id]
inner join sys.indexes ind on ind.[object_id] = mn.[object_id]
inner join sys.schemas S on tbl.schema_id = S.schema_id
where [database_id] = db_id() and mn.avg_fragmentation_in_percent > 40
order by mn.avg_fragmentation_in_percent desc

while exists(select top 1 tabName from #frag)
begin
declare @name as varchar(200), @sql varchar(1000)
select top 1 @name = tabName from #frag
set @sql = ‘ALTER INDEX ALL ON ‘ + @name + ‘ REBUILD’
select @sql
delete from #frag where tabName = @name
exec(@sql)
end

drop table #frag

I am using the following query to get my index details to reorgnaize or rebuild them

SELECT
OBJECT_NAME(B.OBJECT_ID) as TableName, b.name as Index_Name,
CASE
WHEN ps.avg_fragmentation_in_percent > 30 THEN ‘REBUILD WITH (,PAD_INDEX=OFF,STATISTICS_NORECOMPUTE=OFF,ALLOW_ROW_LOCKS=OFF,ALLOW_PAGE_LOCKS=OFF,ONLINE=ON,SORT_IN_TEMPDB = ON,MAXDOP=2)’ –FOR ONLINE ADD USE THIS ‘REBUILD WITH(ONLINE = ON)’
ELSE ‘REORGANIZE’
END AS INDEX_OPTION,avg_fragmentation_in_percent as Fragmentation_Size,
ps.Page_count as TotalPage
FROM sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL, NULL, NULL) AS ps
INNER JOIN sys.indexes AS b ON ps.OBJECT_ID = b.OBJECT_ID
AND ps.index_id = b.index_id
WHERE ps.database_id = DB_ID() AND b.name IS NOT NULL AND ps.avg_fragmentation_in_percent > 10
ORDER BY TotalPage desc

But its making my machine hang, I am unable to do anything after executing this. Could we do some improvement in this query.

Why the script would not return any indexes and their statistics e.g % fragmented? Doe this mean ther are none indexes in this datbase thar are fragmented even a small percent. DO i need to run something else before i run this script.

You can do this to find out the ID:

USE yourdatabase
SELECT DB_ID() AS [Database ID];
GO

Do I have to replace the exact Database name etc somewhere in this script.

Thanks