poor performance in insert queries

 Hi,

       I have two sessions. The session A make  million selects queries on an table FS_DADOS to export to an excel and the session B make many inserts and deletes on table SAIDA_NF.

       Well, when these sessions run together, the session A process his selects normally, but the session B hungs in the insert queries with the latch: shared_pool contention.  The insert query runs in two minutes when it runs alone. When the session B runs together session A, the same insert query takes over 40 minutes.

  Is there a workaround or solution in this cases?