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The Index Analyzer tool helps you evaluate SQL Server index= ing. With this tool, you can view indexes contained in a specific table, or= view index properties and performance statistics across a SQL Server = instance.
By default, Index Analyzer connects to the specified SQL Server instances = using the credentials of your currently logged on Windows account, and then= collects information and performance statistics about each index.
Selectivity is a critical statistic for analyzing index performance. How= ever, retrieving selectivity from SQL Server is a time-intensive operation.= To analyze selectivity across all indexes on the specified instances, clic= k Load Selectivity while loading Statistics befor= e you begin. To view selectivity values on a few indexes, load the other in= dex statistics first, then select the indexes you want to analyze and click= Load Selectivity.
The following index statistics are available for viewing in the Index An= alyzer tool results:
Provides the percentage of rows modified = since statistics were last updated.
If this percentage is high=
em>, then SQL Server is using outdated information to make optimiz=
ation decisions. A high percentage can negatively impact system performance=
.
You can reset this value by updating the index statistics.
Percent of Updates to Total Accesses. If = an index is updated often, then the usefulness as an index is offset by the= overhead of keeping the index updated.
Indicates which columns were affected by = the statistic.
Indicates whether the index is clustered.=
Provides the name of the database contain= ing the index.
Indicates whether the index is disabled.<= /p>
Provides the Fill Factor used to create t= he index.
Provides the name of the index.
Provides an estimate of how likely it is = that SQL Server uses the index based on the following criteria: Selectivity= , % Rows Modified, and % Updates to Total Accesses.
Indicates when SQL Server last updated st= atistics for the index.
Provides the number of lookups performed = on the index.
Provides the number of 8K pages used by t= he index.
Provides the number of rows in the index.=
Provides the number of rows modified sinc= e SQL Server last updated these statistics.
Provides the number of scans performed on= the index.
Provides the number of seeks performed on= the index.
Indicates the statistical uniqueness of e= ach row of the index. Selectivity is calculated from the index density stor= ed by SQL Server (Selectivity =3D 1 - Density). Low Selectivity may negativ= ely impact system performance.
If no statistics are stored i= n SQL Server, the value for this column is "No Statistics Ava= ilable".
Provides the physical size of the index i= n bytes.
Provides the name of the table containing= the index.
Sums the total number of times the index = is accessed (Seeks + Scans + Lookups + Updates).
Provides the number of updates to the ind= ex.
The following column statistics are available:
Indicates which columns were affected by = the statistic.
Provides the name of the database from wh= ich the statistic was generated.
Provides the number of rows that were upd= ated, inserted, or deleted.
Indicates the statistical uniqueness of e= ach row of the statistic. Low Selectivity may negatively impact system perf= ormance.
Provides the name of the SQL Server = statistic calculated for this column.
Provides the name of the table from which= the statistic was generated.