Index becoming unusable again and again

The application team was complaining about slow response. My reaction was to run a few queries to check the response. The SQL seem to be slow. The explain plan showed that the indices were not getting hit and the queries were doing full table scan. On checking the table structure the indices were Invalid (Two

Full table scan not hitting an index

What do you say to that? Dears; Kindly bee Informed after I ask you to Analyze below tables: b.pay, b.rec, b.trans When I chek above tables “Table Access full” appears so would you plz chec it agai why after analyze and re index tables still full. Of course :(:( …!!! Why would select all from