A tool for an approach and mechanism for calculating and configuring memory mapping of trend log objects in a system, such as an HVAC. It may incorporate determining available memory of a controller for trending a unit of equipment of a system. A calculation of available records may be made for configuring and using a trend. The calculation may be made in view of the controller memory and parameters including buffer size, log interval and retention time. A change in parameters may cause a recalculation of available records. The “available record” terms may be regarded as being in a user-understandable format. The format may be intuitive. Anomalies of trends of equipment may lead to spotting issues of the equipment.