Joined: 06 Jan 2004 Posts: 247 Location: Hyderabad
What u read is correct.Determining the method of access or access path(watever we call)is an automatic function of DB2. This function is performed during the bind process for static SQL or during execution time for dynamic SQL.
Access path is nothing but the order in which records in a database file are processed.Access paths reduces the system overhead.Access path selection criteria is based on the statistical information which is stored in db2 catalog.These catalog statistics are updated by execution of the RUNSTATS utility. DB2's determination of the most efficient access paths is dependent on the accurate and realistic statistics of this catalog.Optimal access path selection is important to resource utilization.Access path selection may include the use of RUNSTATS, rebinding, and EXPLAIN.
If the runstats is incomplete and doesn't reflect the current state of data there are more chances to select a very bad access path instead of good one.So we should see that always db2 catalog has current statistics.