Hi Sai,
In general at Prod, the data which was 90 days old, prefer delete from PSA. in that way you can plan in quality system and try to delete data from PSA and change log deletion thru process chains.
Normally we use DSO where data source won;t support delta. in that cases you can delete old requests from PSA.
Before doing make it proper steps and check with yout TL or PM. once they said ok go further.
Thanks