You will have to increase the retention time of Archive Manager database. The default value is 45 days. But increase it with caution, because it will increase the DDMdb database size and would affect the performance.
After changing the value to 180 days, you will have to restart the Archive Manager.
Make sure you have free disk space before increasing the MAX_EVENT_DAYS and MAX_STAT_DAYS.
Archive Manager Resources - CA Spectrum - 10.1 to 10.1.2 - CA Technologies Documentation
Archive Manager resources are settings that control how historical records are processed. These resources also enable the Archive Manager to communicate with the SpectroSERVER and DDM databases.
Archive Manager resources are defined in the .configrc file, which is located in the $SPECROOT/SS/DDM directory. The resources are listed in the form “resource = resource_value”, as shown here.