The Run Statistics utility is used to collect information about the organization of your table structures. That information is used by the DB2 Optimizer to provide the fastest access for a query to the underlying data.
When a SQL operation is executed the DB2 Optimizer examines the catalog tables, checks for the condition of the indexes, and performs its analysis. The more up to date the information, the more likely it is that your query will use the best access path; and the more complex the query, the more important it is to have the latest information as the number of possible paths grow exponentially.
You run the Run Statistics utility using the Run Statistics dialog from the Control Enter menu with the appropriate fields selected. You can also use the RUNSTATS command from the Command Center or from the Command Line Processor, specifying the table name(s) and index(es) name. You need SYSADM, SYSCRRL, SYSMAINT, DBAMN authority or CONTROL privileges in order to invoke this command. In either case the utility updates the system catalog tables for the table(s) named.
You should use the Run Statistics utility when a large number of operations have been performed on a table's rows. These operations can be single row transactions such as INSERT, UPDATE, and DELETE. Or they can be batch operations such as an IMPORT or load against a table. Anytime you fundamentally reorganize a table by creating an index or reindexing it, or by adding or removing columns new statistics should be collected.
About the Author
Barrie Sosinsky (barries@sosinsky-group) is president of consulting company Sosinsky and Associates (Medfield MA). He has written extensively on a variety of computer topics. His company specializes in custom software (database and Web related), training and technical documentation.
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