Query optimization tools: comparison table


PRTSQLINF STRDBG/CHGQRYA STRDBMON Memory-Based Monitor Visual Explain
Available without running query (after access plan has been created) Only available when the query is run Only available when the query is run Only available when the query is run Only available when the query is explained
Displayed for all queries in SQL program, whether executed or not Displayed only for those queries which are executed Displayed only for those queries which are executed Displayed only for those queries which are executed Displayed only for those queries that are explained
Information on host variable implementation Limited information on the implementation of host variables All information on host variables, implementation, and values All information on host variables, implementation, and values Limited information on host variable values
Available only to SQL users with programs, packages, or service programs Available to all query users (OPNQRYF, SQL, QUERY/400) Available to all query users (OPNQRYF, SQL, QUERY/400) Available only to SQL interfaces Available only through Visual Explain in Operations Navigator Database
Messages are printed to spool file Messages is displayed in job log Performance rows are written to database table Performance information is collected in memory and then written to database table Information is displayed visually
Easier to tie messages to query with subqueries or unions Difficult to tie messages to query with subqueries or unions Uniquely identifies every query Repeated query requests are summarized Easy to see the relationship between the provided information and the query


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