Although the system has some ability to extrapolate reasonable estimates for rows added since statistics were last collected, statistics that are far out of date (stale) may be worse for Optimizer query planning than having no statistics at all.
Recommendation: Use the THRESHOLD option for COLLECT STATISTICS so the system automatically determines if statistics are stale and need to be recollected or if recollection can be skipped. See “Skipping Unneeded Statistics Recollection with the THRESHOLD Option” on page 254.
Note: If the current statistics are stale, but you do not want to recollect them because of resource contention, you can temporarily drop the statistics using the DROP STATISTICS command, and use the default statistics automatically collected by the system. However, you should recollect new statistics at the earliest opportunity.