Estimates the reduction in the average size of rows if you enable vardecimal storage format on a table. Use this number to estimate the overall reduction in the size of the table. Since the statistical sampling is used to compute the average reduction in the rowsize, regard it as an estimate only. In rare cases, rowsize may increase after enabling the vardecimal storage format. Vardecimal storage format is available only in SQL Server Enterprise, Developer, and Evaluation editions, starting with SQL Server 2005, Service Pack 2.
This feature will be removed in a future version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature. Use ROW and PAGE compression instead. For more information, see Creating Compressed Tables and Indexes. For compression effects on the size of tables and indexes, see sp_estimate_data_compression_savings (Transact-SQL).
The following result set is returned to provide current and estimated table size information.
decimal (12, 2)
Represents the length of the row in fixed decimal storage format.
decimal (12, 2)
Represents average rowsize when vardecimal storage format is used.
Number of rows in the table.
Use sp_estimated_rowsize_reduction_for_vardecimal to estimate the savings that result if you enable a table for vardecimal storage format. For instance if the average size of the row can be reduced by 40%, you can potentially reduce the size of the table by 40%. You may not receive a space savings depending on the fill factor and the size of the row. For example, if you have a row that is 8000 bytes long and you reduce its size by 40%, you can still fit only one row on a data page, resulting in no savings.
If the results of sp_estimated_rowsize_reduction_for_vardecimal indicate that the table will grow, this means that many rows in the table use nearly the entire precision of the decimal data types, and the addition of the small overhead needed for vardecimal storage format is greater than the savings from vardecimal storage format. In this rare case, do not enable vardecimal storage format.
If a table is enabled for vardecimal storage format, use sp_estimated_rowsize_reduction_for_vardecimal to estimate the average size of the row if vardecimal storage format is disabled.
The following example estimates the rowsize reduction if the Production.WorkOrderRouting table in the AdventureWorks2008R2 database is compressed.
USE AdventureWorks2008R2; GO EXEC sp_estimated_rowsize_reduction_for_vardecimal 'Production.WorkOrderRouting' ; GO