!System Preference
The REP CACHE EXPIRY preference defines how long the report output is available in the Oracle Report Server Cache (in minutes) HOWEVER Oracle has this expiry time defined from the “Launch” of the report and not the “Completion” of the report so if you set this too little the report output may expire before you are able to see it. 

RECOMMENDATION – set it to 60 initially and review the run time of reports over a period to see whether it needs to be raised (or lowered). 

This preference may be set by site ([IMST]}.