Do the rsrv test make sure the object is consistency and have properly maintained.
Check the size of Dimention table of cube it can be seen by using the F.M i.e. SAP_INFOCUBE_DESIGNS, The ratio should be like 20 % of fact table.
Compress the data present in cube level this help in better read operations.
Do the house keeping check weekly like deleting the old psa request say 7 day old and deleting the change log table it will ease up some memory that u can check in DB02 before and after doing the house keeping act. This will increase the performnace.
make sure only important characteristic are there in rows all other characteristic should be moved to free charac in query designer.
Before doing any load to Infoprovider then do the practice of deliting the index before and load and creating th eindex after load.
Try restricting the query to particluar 0infoprovider if possible.
Go to rsrt check the infrpovider performance tab.
if required create the aggregates
Regards,
Akshay