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 TuneTable does the same job like UPDATE STATISTICS in MS SQL Server. During its evaluation of a query, the query optimizer uses these statistics to estimate the cost of using an index to satisfy the query. Having good statistics for table cardinality and column cardinalities is very importent.
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ExtentSize is the approximate number of rows in the table. The number does not need to be exact, just relative to the size of other tables. The Query Optimizer uses ExtentSize to find the starting table for queries. |
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The Selectivity value for a column is the percentage of rows within a table that would be returned as a result of query searching for a typical value of the column. A measure of distinctness of the data |
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Bitmap indexes consist of a bitmap (bit vector) for each distinct column value. Each bitmap has one bit for every row in the table. The bit is on if the related row has the value represented by the bitmap. |
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Separating data and log is still a good idea, so store the Journal, WIJ, SYS and CacheTemp on separate disk controllers from each other and from the main DB(s).
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