You can use SAPDBA for Informix to identify tables where the statistics deviate from the current (that is, correct) values by more than a certain threshold. For more information, see Update Statistics with SAPDBA.

• SAPDBA is installed correctly. Refer to SAPDBA Setup.
• You know how to use SAPDBA and have logged on. Refer to Starting SAPDBA.

Choose Update Statistics ® Tables with Deviation in SAPDBA for Informix.

The first screen you see allows you to enter the deviation in percent. The recommended default value is 10%. Only tables where the deviation is equal to or greater than 10% are displayed in the subsequent report.

• If you enter a low threshold value for deviation (say 5%), even tables where the statistics deviate only slightly are displayed in the report.
• If you enter a high value (say 25%), only tables where the statistics deviate greatly appear.

• If you choose one of the numbers on the left of the report, you can perform update statistics on the single table selected. Refer to Updating Statistics for One Table with SAPDBA. With this action, you can have SAPDBA update the old statistics information for the table with the current value.
• The deviation [%] field is the percentage difference between current_rows and statistic_rows. A question mark is displayed in this column when the value of statistic_rows is zero and the percentage cannot be sensibly derived.
• The current_rows field is the correct, up-to-date number of rows in the table (dating from the last time the statistics were updated).
• The statistic_rows field is the less up-to-date number of rows held in the table’s statistics.
• The deviation field is the absolute difference between current_rows and statistic_rows.
• Sort order for the report is current_rows followed by table name.

For more information about printing the report, see Printing a SAPDBA Report.