Requirements

UPDATE STATISTICS collects statistics for opaque data types only if you have defined user-defined routines for statcollect( ), statprint( ), and the selectivity functions. You must have Usage privilege on these routines.

In some cases, UPDATE STATISTICS also requires an sbspace as specified by the SYSSBSPACENAME configuration parameter. For information about how to provide statistical data for a column, refer to the IBM Informix DataBlade API Programmer's Guide. For information about SYSSBSPACENAME, refer to your IBM Informix Administrator's Reference.

Using the LOW Mode Option

Use the LOW option to generate and update some of the relevant statistical data regarding table, row, and page count statistics in the systables system catalog table. If you do not specify any mode, the LOW mode is the default.

In Dynamic Server, the LOW mode also generates and updates some index and column statistics for specified columns in the syscolumns and the sysindexes system catalog tables.

The LOW mode generates the least amount of information about the column. If you want the UPDATE STATISTICS statement to do minimal work, specify a column that is not part of an index. The colmax and colmin values in syscolumns are not updated unless there is an index on the column.

The following example updates statistics on the customer_num column of the customer table:

UPDATE STATISTICS LOW FOR TABLE customer (customer_num)

Because the LOW mode option does not update data in the sysdistrib system catalog table, all distributions associated with the customer table remain intact, even those that already exist on the customer_num column.