How SAPDBA Performs Update Statistics 

SAPDBA for Informix performs update statistics on columns using the following defaults:

SAPDBA also performs update statistics at "table level" to update the size of indexes, number of rows and so on (this is done at level low).

For a table with multiple indexes where the indexes are similar, SAPDBA behaves as follows:

A table has two indexes as follows:

Index 1: Columns A, B, C, F, G, and X

Index 2: Columns A, B, C, E, H, I, and X

Update statistics is performed at level high for columns A, B, C, E, and F and at level medium for columns G, H, I, and X.

SAPDBA allows you to update the statistics of a table when:

 

See also:

Informix documentation