The data_engine controls the age of the data stored in the raw (RN_QOS_DATA_nnnn) and historic (HN_QOS_DATA_nnnn) tables.
The sla_engine will only use raw QoS data located in the RN_QOS_DATA_nnnn tables for calculating SLOs and SLAs.? If a calculation time period exceeds the age of the stored raw data, then it will not be possible to calculate this SLA.
The SLM portlet uses historic QoS data from the HN_QOS_DATA_nnnn tables when displaying QoS data used in an SLA calculation.?
If the data_engine is configured to keep raw data for 90 days and historic data for 180 days, then it will not be possible to calculate SLAs from 4 months back since the raw data has already been removed.? However, it is possible to see up to 6 months of historic QoS data when viewed in the SLM portlet for the specific QoS metric.